Please visit our Sponsors
More FAQs about ORP, Ozone, Ozonizers Measuring

Related Articles: Reduction Oxidation Potential, RedOx: A Very Valuable Tool For Assessing, Assuring Maine Aquarium Health, ppt. presentation, Part 1, Part 2, Part 3, by Bob Fenner, Physical FiltrationRedOx,

Related FAQs: Ozone, Ozonizers 1Ozone, Ozonizers 2 Ozone 3, Rationale, System/Selection, Application/Installation, About Dryers, Maintenance/Repair, Reduction Oxidation, & Marine Test Gear 1, Marine Test Gear 2, Marine Water Quality, Marine Water Quality 2, Marine Water Quality 3,

No consensus... but something about 300 plus on the low side... 400-425 mv/micro-Siemens on the high is about right

Re: Hydrogen peroxide; re ORP       01/17/19
Good afternoon Bob. I just have a follow up question regarding dosing hydrogen peroxide. In our earlier messages you said to monitor my ORP while dosing.
<Yes; can drop immediately and dangerously low>
What I am finding is that the HP almost immediately shaves 80-100 points off my ORP reading. I normally run at about 360-380 ORP and within minutes after dosing HP it drops to 300-280. It takes about 6 hours to climb back up to the 360-380 range. What exactly am I looking for with the ORP while dosing HP?
<This exactly. I would NOT have ORP drop more than 100 units (micro-siemens/cm.) per dose>
Thank you,
<Welcome. Bob Fenner>
Re: Hydrogen peroxide      01/17/19

Interesting. I didn’t realize a low ORP was dangerous. I’m fully aware of the danger of a high ORP. What happens when it gets to low?
<This may seem (overly) dramatic; but all life ceases. Really, a steady, reasonable ORP/RedOx state is a good measure of a system's capacity to support life. B>
Thank you

Basic Questions: Measures of water quality, value     4/16/14
How's it, Bob?
<Fine, thanks>
I was at my local LFS the other day, and inquired about ORP and PH. He has some pretty darn nice displays, and probably has the best looking coral selection in the state. He seems to know his stuff, however I became
confused during our convo.
When I asked about measuring ORP and PH, he stated to me those were useless.

He said to me the PH in seawater is set to stay at a given PH, and measuring it will only lead people to chase the perfect ph by adding buffers that will throw off other elements. He told me in a reef tank, the two things to measure are Alkalinity and Calcium, and if those are good, your PH will be in line as well.
<Interesting point of view... I myself am much more a bigger fan of measuring alkalinity than pH... but both can be useful windows; provide views into water quality, changes>
He then showed me his reef set ups, and stated there were no PH monitors nor ORP.
Could this be remotely correct? I have always read you had to monitor them, however hearing this from him, has me puzzled. Says the only time he measures PH is during freshwater dips.
<You can easily search, read my opinions on these... even just on WWM.
RedOx is a supremely important and useful measure... ALL public aquariums utilize O3... Most all marine wholesalers, the collecting stations I've had a hand in devising. B>

Re: after Ich outbreak -update right side of tank     8/3/13
Hello Mr. F
I guess I was trying to send you another picture with another side of my tank...
Anyway, my Neptune Apex has just arrived, and I was wondering what range of values should I set to the ORP for my AquaMedic 100 mg ozone which is connected to my skimmer.
Thank you,
<425 on the high side, 350 on the low. Bob Fenner>

Asking about orp controller      4/25/13
I'm Natra, student from Malaysia. May i ask something related to ORP controller. in my experiment, i need to use this equipment. however, in the first experiment i need to measure the ORP reading in the water (without ozone). i get the reading 600mV.
<Whoa; this is high!>
should be, the reading without ozone in the water is 0mV, right?.
<Mmm, well; not tap/mains water... Distilled that has been totally degassed should be close to 0 mV>
 what  should i do to overcome this problem.
<Your meter needs to be calibrated... with at least two known solutions.
Look for the manual that came w/ the meter; or look it up, maybe contact the manufacturer... via the Net>
i really need your help as soon as possible.
thank you.
<Sama sama, Bob Fenner>
Re: re: Asking about orp controller     4/25/13

i forgot to ask. if i used the tap water. what should the reading on the orp.
<Can't tell... varies by region, water source, treatment... Not zero though. All municipal waters have conductive materials, salts et al. in them...>
 continue with my experiment. at the first experiment without injection of ozone into the water, iget the very higher reading. but, when i inject certain amount of ozone into the water, the orp reading becames decreased.
so, can u give any suggestion toward my problem.
<.... You need to know the ORP of your source water... contact the agency that supplies it, use another meter to check the accuracy, precision of yours. BobF>
i really need your help as soon as possible.
Re: re: Asking about orp controller     4/25/13

u can speak in Malay.
<Only a little. Polite interrogatories>
the problem right now, i don't know which manufacturer and i also haven't the manual. what can i do.
how to calibrate the meter.
can u teach me.
<I cannot w/o knowing the make, manufacturer of the device... Again, you need at least two standard solutions of known RedOx potential to calibrate.
i really need your help.
Re: re: Asking about orp controller     4/26/13

i have another question, today i need to replace the tap water to distilled. Water. however, the orp reading are 300++mV. so, it is problem with my orp right.
<... not necessarily, no. There is a simple adjustment (likely a dial) to zero this>
 about the manual of this equipment, i can't find it. because the. student before this, missed that manual.
can u help me.

High ORP and UV 3/27/12
Hi WWM Team,
<Hello Brad>
I have a question regarding high ORP and using a UV sterilizer that I couldn't find a direct answer on after searching the site (and reading some great forum posts especially http://www.wetwebmedia.com/redoxfaq.htm ).  I know that ORP / RedOx is a complex relationship impacted by many factors (http://reefkeeping.com/issues/2003-12/rhf/feature/index.php ).  From what I've seen on the site (especially from Anthony) the recommendation is to keep ORP below 425mv.  I'm not running any Ozone (have in the past, but not in the last few months), I'm only using UV in my tank which I know can have an impact on ORP.  So the question is, if my ORP is at 415mv should I be turning off the UV?
<I would first check the calibration of the ORP meter.  A 415 reading is a little high, especially with no ozone being generated.  The UV does produce some but I do not believe it would take it to that level.>
I know with Ozone you want to keep it below 400 and definitely below 425 based on what I've seen suggested in the RedOx FAQ, but what about if you're not using Ozone, just UV + Protein Skimmer?  I can turn off the UV automatically in combination with my ORP probes (I have two and they both read about the same within 15mV throughout the tank / sump so I don't think I'm getting bad readings.)
<I would check both probes with a calibration solution just to be sure.>
Everything seems fine/happy at 415mV but I'm a bit concerned about leaving the UV on if it's going to alter the water quality and hurt any of my fish/inverts, or if since I'm not using Ozone I should just keep using the UV as is without much concern for the ORP?  If I should be concerned, at what ORP level would you shut off the UV?
<An ORP of 350-375mv would be my target.  Bob may comment here as well.>
Thanks much!
<You're welcome.  James (Salty Dog)>

Re: hyposalinity and Ich, RedOx/ORP measure   3/2/12
Hi Bob,
Are the RedOx meters and ORP meters the same thing?
 I am trying to order one like you suggested but its called an ORP/PH meter..is that what I need for RedOx monitoring?
<Will work; yes>
<Welcome. BobF>

Re: hyposalinity and Ich, RedOx meter sel.    2/21/12
Hi Bob
Sorry for the twenty questions....but is there a particular RedOx meter you recommend? Is one better than another? I don't want to buy a piece of junk and have no experience with any meters actually :)
<The inexpensive Milwaukee and Hanna meters are faves... they're accurate and precise enough... BobF>

Ozone Questions... reduced algal growth effect, placement of ORP probe 8/27/11
Hi guys
<Hello Matt>
As usual you are my first port of call when it comes to my fish dilemmas!
Firstly, I have been running ozone through the skimmer in my sump for several months now and have noticed a significant decline in the growth of desirable algae in the sump (Caulerpa primarily); is this to be expected as there will be less organic compounds for them to feed on?
<Is the whole idea.>
Also I am seeming to have to clean the probe tip on my ORP meter daily in order to get accurate readings. It seems to keep getting gunk on it which lowers the readings. It is in the main tank in a 'quiet' corner, should I place it in a higher flow area? Is this a fairly common issue?
<Best to place in the sump, away from a light source and where water is moving.>
Thanks so much as always.
<You're welcome. James (Salty Dog)>

More Questions About Ozone Use - 04/30/09
Dear Eric,
<<Hiya Andy>>
Sorry to bother you again, but I have a few follow up questions regarding ozone.
<<No problem'¦and not a bother>>
First, I did buy the Red Sea Aquazone Deluxe.
I know you believe there are better units out there, and I don't disagree, but I thought a brand new 100 mg/hr unit with all the fixin's for $200 less than retail was a good start for me.
<<Sounds fine (after all'¦it is 'your' money)>>
Now that that's out of the way . . . I have an AquaC EV-180 without the special fitting and I corresponded with AquaC about how to run the ozone through the skimmer. As instructed, I drilled a hole next to the air intake, inserted silicone tubing in the hole and sealed it with silicone gel.
<<'¦gel? As in 'sealant' I presume'¦>>
Thinking ahead, which is something I don't always do, I decided to affix only a small length of tubing to the skimmer, which I connected, using a brass barb, to the longer piece that attaches to the ozonizer so I can disconnect and service the skimmer.
<<Mmm, it may be a small risk but I would replace the brass barb fitting with a plastic barb fitting (for fear of liberating copper ions via the ozone), or better yet, a JACO connector>>
First, although the unit was unused and the manual says the Red Sea ORP probe is pre-calibrated to work with the controller,
<<Always best to calibrate any such new equipment/probes>>
I want to confirm that my probe is in fact calibrated.
<<You can only do this with a calibration solution of known value>>
My ORP reading is 190, but I do a 15% water change (RO/DI) every two weeks, employ a good skimmer that I service regularly, have a 30g refugium with Chaetomorpha, have a shallow substrate bed (1/2" or less), and have a pretty light bioload, so I'm skeptical of a reading that low.
<<Hmm'¦does sound/seem 'low''¦and I hate to say'¦but maybe why this unit was sold/sold so cheaply?>>
Right now, I have the probe mounted in my sump where the water enters from the overflow, so there is a lot of circulation/flow there, but I did notice that when I had the probe in my tank, the ORP was measuring at about 230.
<<Readings can fluctuate quickly and are probably influenced by the position/location of the probe>>
The manual says that you can get different ORP readings at different locations and to search around,
but it also says to place the probe in a dark place, like the sump, to avoid fouling.
<<It may require more maintenance'¦but I prefer to keep my probe in the tank (near those affected most)>>
Maybe the reading is correct, but maybe not . . . Do you know if I can just use any ORP probe calibration fluid?
<<Any fluid with a known value in mV, yes>>
Second, and I'm sure this varies with conditions/ozonizers,
<<And environments/tanks>>
but how long does it generally take to see a change in ORP once you start using ozone?
<<As long as the unit is large/efficient enough to make a difference'¦within a day or two for sure>>
Third, is it absolutely essential (for safety) to filter the air exiting the skimmer with activated carbon to eliminate any excess ozone?
<<Not in my opinion (I don't do this). The molecular interaction/action of the skimmer itself will do much to remove/use the ozone'¦and residual ozone is not much if any of a threat with most of these hobby units if utilized/installed correctly, in my opinion. But do consult others re'¦and decide what you feel comfortable with>>
When Bob F spoke about this, he basically stated (I'm paraphrasing, and hoping I got it right) that, given the small amount of ozone we employ in aquaria and given that ozone so readily dissipates/metabolizes/whatever, this really isn't a concern,
but if you want to be 100% safe, go ahead and filter the air.
I can definitely smell some ozone in the air when I'm around my tank--nothing overpowering or anything, but it's there. I've asked the good people at AquaC, but I'm scratching my head as to how I might go about filtering the air leaving the water exit valve (which, other than the collection cup drain, is the only place that ozone can escape)--the EV-180 manual says not to restrict the flow of this water. If I stick a filter bag full of carbon over the exit valve, the flow is going to be restricted. Although the restriction may be small at first, I anticipate that the bag will foul over time and the restriction will become more significant.
<<Agreed'¦ But you can simply place a bag of carbon in the sump 'under' where the water falls from the skimmer'¦and another atop the collection cup vent holes (if it has such). I really don't think you have much to fear here'¦but as stated, do what 'you' are comfortable with>>
Thanks again for all of your help.
<<Always welcome'¦ EricR>>

R2: More Questions About Ozone Use - 05/03/09
Okay, Eric, I am a complete moron.
I didn't realize that you have to take the plastic black cap off the end of the electrode!
D'oh! The cap has a hole in it and a white plastic insert, and the Red Sea instructions do not clearly state that the cap should be removed. I thought it odd that the cap should stay on. Oy!
<<Hee-hee! Sometimes the simplest of things'¦'¦'¦'¦>>
Now I am getting good readings.
Andy Bulgin
<<Excellent my friend'¦though 'I' would still stick the probe in some calibration fluid just for my own 'knowing.' Cheers mate'¦ Eric Russell>>

R2.5: More Questions About Ozone Use, meas.  - 05/04/09
Yes, Eric, it is often the simple things that doom us to failure!
<<Or at least delay success/satisfaction>>
I agree with your advice, which is why I ordered 450 mV calibration fluid--the electrode is measuring about 495 mV. I cleaned it using the cleaning solution, but it didn't change the reading. So, ordered a Pinpoint replacement probe.
<<'¦? Does this unit not have a means of 'calibrating' the electrode? Even if it doesn't state it in the instructions, the unit likely has a potentiometer located somewhere (if you know what to look for) that allows voltage adjustments to calibrate the probe to the calibration fluid. Unless there's an adjustment screw located on the outside of the unit'¦or instructions with the unit stating where to look otherwise'¦I'm reluctant to send you looking/probing around inside the casing of the ozonizer for fear of electrocution'¦even if unplugged, some components of these high-voltage units may still 'hold a charge.' If there's nothing in the instructions, you can try contacting the company about calibrating the probe (I can't imagine a unit that wouldn't allow this)'¦or maybe find an electrician to have a look>>
I don't know if the 2-year shelf life of these probes applies whether or not it is used, but it appears that this one needs to be replaced.
<<Normally the probe does not need replacement until it won't 'hold' the calibration'¦though I have had bad ones right from the box that wouldn't take/couldn't hold calibration>>
Thanks again for your many, many helpful responses. Until my next dilemma...
Andy B
<<Always a pleasure'¦ EricR>>

R3: More Questions About Ozone Use - 05/04/09
The manual says to chuck the probe (a Reagecon Ag/AgCl electrode) and replace it once its reading goes above 475 mV or below 425 mV. Says nothing about adjusting.
<<You know, you're right'¦I'm mixing up my meters/monitors/controllers here. Though there's still something nagging at the back of my mind (gonna have to take another close look at my Milwaukee ORP controller tonight), replacement of the probe on ORP units is generally the only option offered when the reading/calibration is out of whack. My apologies for any confusion. Eric Russell>>

Ozone causing a drop in ORP - 07/19/08 Attached is my design for my ozone addition to my sump and skimmer. <I see this> I fired up my ozone this morning at 9am and since then I have noticed a drop in ORP. Can you come up with any theories as to what would cause a drop in ORP w/ ozone? <Mmm... did you add food, some livestock... additives about this time as well?> I have shutdown the ozone until we can get to the bottom of this. Graph of my ORP: http://fuse44.fusemail.net/aqua/index.html?prevtype=&view=467 <Mmm, the first chart looks fine... the third and fourth have some (I believe) spurious readings> total tank volume: 400gallons sump volume: 70 gallons skimmer: RPS-3000 recirculation ozone: Ozotech Poseidon <A very good product> Best Bryan <Well... I would re-route the ozone into your skimmer, dump the water from it as is shown back into the sump... try "cranking it up" when you can be present for an hour or two... see if there is an upward trend in ORP. Bob Fenner>

Re: ozone causing a drop in ORP - 07/19/08 Hi Bob, <Bryan> Thanks, the Ozotech is routed directly into the intake of the recirc pump of the skimmer, and the water from skimmer is dumped back into sump. I did not add any new livestock/food/anything different during the ozone addition. <I see> I have confirmed the Ozotech is working as I can smell the ozone, with the Ozotech on full the trend is not upward. Yesterday I left it running for several hours and the ORP stayed near the same. <Bizarre... and am sure this is an adequately "sized" unit... 1,000 mg/hour or more...> Do we need to leave this on for several days before we see any trend at all? Best Bryan <Shouldn't, but... is there a huge amount of biomass, processing going on in this system? Do you have another probe you might use to "check the checker" here? Bob Fenner>

Re: ozone causing a drop in ORP 07/20/2008 Hi Bob, <Bryan> The tank is fairly loaded without going into detail, I wouldn't say overloaded. <Okay> I change water fairly frequently, probably more than most people, and skimmer production is constant but not significant. I do have another ORP probe I can check with but it's older and honestly probably more inaccurate than the current one. <Not a worry... just need to see if these "move" in accordance with each other> I am using a Neptune controller w/ ORP probe purchased w/ the Neptune. <Usually reliable> Not sure what's going on here, I will probably get some test solution to check my probe before I run ozone long term. Right now I am to frightened to leave it on for to long w/o knowing what is at play here. Thanks <Not likely problematical either... Do please follow-up with me here. Cheers, Bob Fenner>

Large ORP Drop 4/28/08 Hello, <Hi Bryan> I experienced a major ORP drop while I was away on vacation on my 400g tank/sump. Typically my ORP stays right around 400 +/- 10-20. It started dropping to around 350 and then dropped to 150 almost instantly. Since then it has been slowly moving back up, it is now at 214 after a 50g water change I performed today. Upon my return I inspected the ORP probe and found no debris and the probe looked physically OK. Parameters look great, ammonia: 0ppm, nitrates: 0ppm, nitrites: 0ppm, calcium >400, dKH 11. I perform water changes of about 50 gallons twice a week. See graph of ORP: http://fuse44.fusemail.net/aqua/index.html?prevtype=&view=467 What's your guess, faulty ORP probe or a real result? and if real, why such a dramatic shift so quick? <An undiscovered dead animal could cause this <<No... not this sudden drop... Too much in the period... see the graphs... the data is collected every minute. RMF>>  along with an additive you may have put into the tank, but I'm thinking probe. Best to get a packet of 400mv calibration fluid and check the probe. You may be interested in reading here along with the linked files above. http://www.wetwebmedia.com/redox.htm James (Salty Dog)> Best Bryan

Re: Large ORP Drop 4/30/08 Thanks James, <You're welcome.> all of my fish are accounted for, but could be snails. If I had an ORP drop this significant due to bio, wouldn't I see ammonia, nitrites or at least elevation in nitrates? I also would have expected a more gradual decline over a few hours or day or 2. <Yes, sorry, but I erred in my response. A dead animal would not cause an immediate drop such as you have experienced. I'm now wondering if you didn't experience a very short loss of power. Have your readings been steady since that event?> I will check the probe. <Good.> Thanks!

Ozone Generator and ORP Monitor Questions -- 02/12/08 Hello crew, <<Howzit, Dave!>> I just purchased a Poseidon ozonizer from Ozotech. <Ah! A great piece of gear'¦ I use their OZ4PC10-V/SW 300 mg-hr ozone generator on my 500g (en toto) reef system. This brand is more costly than the 'usual' hobby generators, but also better built/more efficient/longer-lasting in my opinion. I think I recall Anthony C. commenting on having/using an Ozotech unit for ten years or more now>> I also bought a Hanna ORP/PH combo monitor. <<You may or may not 'need' a controller depending on the size of the system, bioload, etc'¦. But do consider the Milwaukee ORP controller. For not much more than a C-note (sometimes less, depending), you can constantly monitor 'and' control the output of the generator>> My first ORP test with this new instrument gave me a reading of 208mv. I understand this is somewhat low. <<Maybe'¦depends on what was 'going on' prior to testing (e.g. -- feeding). But as a general rule, yes, an average ORP reading between about 330mv and 400mv is desired. You can go a bit higher (max 450mv), but I don't see the need to 'push the limit' here'¦much like with Calcium and Alkalinity levels. Better to reach for a more easily obtainable/stable level within the acceptable limits>> So I turned on my ozonizer to try to bring my levels up. I decided to inject about 100mg/hr. It is my assumption that my ORP levels should have began to climb. <<But not quickly'¦will need time to 'work'>> I took several readings over a 4 hour period and nothing changed. <<I would give the unit a couple days to begin to affect a change>> So I decided to crank my ozonizer up to the max level, and tested my parameters once again after about 45 minutes. Although my ORP level rose to 216mv, I still thought that this was not a significant change for the amount of ozone administered. <<Patience, Grasshopper>> So I turned the ozonizer back down to appropriate levels (80-100mg), and decided to give you guys a stab at my predicament. My thoughts and questions are; should I just monitor my ORP readings and give them more time? <<Indeed>> Is there any way to check and see if my monitor is giving appropriate readings? <<Yes'¦ Calibration fluids can be obtained online>> I'm just concerned about the low reading because I consider myself fairly conscientious and my husbandry practices are up to par. <<Perhaps it is best here if you stop use of the ozone generator and validate the efficacy of the monitor/probe>> Here is my systems layout: 90 gallon AGA, Mega-Flow. AGA model 3 wet dry, with bio-balls removed, instead I'm running 3x Chemi-pure Elites in the bio-balls place. ASM G-3 skimmer, where I'm administering the ozone. 22 gallon DIY refugium, with a 7 inch DSB, lit by 2x40w PC's. The refugium contains Chaetomorpha, and Pom-Pom Xenias. <<Ah'¦an 'animal' filter then'¦neat!>> My display is illuminated by 8 T5's with 4 18k's, 2 10k's, and 2 actinic bulbs. <<Hmm'¦this is likely too much 'blue.' Your corals will do better with more bulbs closer to full-spectrum wave-lengths>> My tank's inhabitants are the following: 1-4in Kole Tang 1-4in Fox Face Lo 1-3in Coral Beauty 2- Cleaner Gobies 1- Mandarin 1-4in Derasa 1-Long-spined Urchin 1-Cleaner shrimp 1-Peppermint Shrimp 10-Astrea snails 10-Assorted Hermits It contains about 100lbs of live rock, and has a 1 inch sand bed. It also contains a couple (2 LPS corals) and 5 SPS frags. I do 10 gallon water changes every week with RO water, and Reef Crystals. I add nothing else except food twice a day. My basic parameters are good, no detectable ammonia, nitrite, or nitrate. SG 1.026, Calcium and Alkalinity levels are within range, and undetectable phosphate. Whew.... I hope that covers it. Any help or suggestions would be greatly appreciated!! <<I do think the ozone generator should have a greater effect than you have witnessed thus far. Verify the accuracy of the monitor, then start out slow and give the unit a couple days between adjustments>> Thanks, Dave Kansas City, MO. <<Happy to share. Eric Russell'¦Columbia, SC>> PS. Still waiting for VOL. 2 Reef Fishes! :) <<Hee-hee! So is Bob!... ER>> <I'll say! RMF... waiting for help, folks who want to "make it happen"... anytime>

ORP Meter Readings 2/9/08 Hi - I recently purchased a handheld Hanna pH/ORP probe. I have a main 75g display with a 20g sump, protein skimmer, calcium reactor, and Kalk reactor, plus a pair of Banggai Cardinals, a Scribbled Rabbitfish, numerous softies (leathers, Zoanthids, mushrooms), and a Bubble Coral. I also have a Pinpoint pH monitor continuously running (ranging from about 8.15 to 8.35). The main reason I purchased this portable monitor was my new quarantine tank. It was just a hassle to move the Pinpoint monitor when I wanted to test water quality in the quarantine. The ORP part of it was a bonus. I have never measured that before in any of the several reef tanks I've owned, but I thought it couldn't hurt. After calibrating the Hanna on pH (much easier to do than the Pinpoint), it matches my Pinpoint perfectly. But my ORP readings are in the 75-85 mV range, which I know is quite low (the ORP probe is factory calibrated, according to the instructions, and cannot be adjusted). I get a similar reading from my quarantine, which measures a pH of about 8.25 and dKH of 10 in virgin saltwater at a SG of 1.025. After doing a little research through your ozone sections, I came across a question which roughly matched mine. The response was that ORP monitors take time (1-2 days) to generate correct readings. Is this just an inherent limitation to a handheld monitor, in which case I should be happy with its pH functionality? Or should I plan on sending it back? Or maybe leave it floating in my sump (it is waterproof and positively buoyant) for a few days to see if it generates a more reasonable reading? Or is there something wrong with my system? I know, a lot of questions. But your response and advice is greatly appreciated. <Ed, I would direct this question to Hanna. Another option would be to purchase the Hanna 400mv ORP/REDOX solution to check your meter. This is available from Drs. Foster/Smith for $3.49, stock number AEL-30804. Their number is 800-443-1160. If you contact Hanna, they may very well send you a packet of the solution free of charge to check the meter's accuracy. James Salty Dog)> James (Salty Dog)> Ed

ORP questions   2/8/08 Hi - I recently purchased a handheld Hanna pH/ORP probe. I have a main 75g display with a 20g sump, protein skimmer, calcium reactor, and Kalk reactor, plus a pair of Banggai cardinals, a scribbled Rabbitfish, numerous softies (leathers, Zoanthids, mushrooms), and a bubble coral. I also have a Pinpoint pH monitor continuously running (ranging from about 8.15 to 8.35). The main reason I purchased this portable monitor was my new quarantine tank. It was just a hassle to move the Pinpoint monitor when I wanted to test water quality in the quarantine. The ORP part of it was a bonus. I have never measured that before in any of the several reef tanks I've owned, but I thought it couldn't hurt. <Is a very valuable measure> After calibrating the Hanna on pH (much easier to do than the Pinpoint), it matches my Pinpoint perfectly. But my ORP readings are in the 75-85 mV range, <Low> which I know is quite low (the ORP probe is factory calibrated, according to the instructions, and cannot be adjusted). I get a similar reading from my quarantine, which measures a pH of about 8.25 and dKH of 10 in virgin saltwater at a SG of 1.025. After doing a little research through your ozone sections, I came across a question which roughly matched mine. The response was that ORP monitors take time (1-2 days) to generate correct readings. <Often so... the membranes have a "break in" period> Is this just an inherent limitation to a handheld monitor, in which case I should be happy with its pH functionality? Or should I plan on sending it back? Or maybe leave it floating in my sump (it is waterproof and positively buoyant) for a few days to see if it generates a more reasonable reading? <Can just soak in a glass... I'd leave outside the system> Or is there something wrong with my system? <The ORP of the new water should not read this low... and I do suspect the ORP of the main system is reading artificially low... I'd hold off for a few days, re-test> I know, a lot of questions. But your response and advice is greatly appreciated. Ed <Bob Fenner>

Ozone Warning Signs   12/11/06 <Hey Bob, just noticed this in TraylessQs, sorry for the delay. -JustinN> >Thank you... is "about the best I/we can do" at this point, to just jam these in this category... Hope you or others can see, fix, re-send. RMF< Hi Bob and Crew <Bob> I have a quick question for you guys. Since I am now using Ozone with an ORP controller, I would like to know what the initial warning signs are that the ozone is damaging either my invertebrates or my fish. <A valid concern> I have a 135 gal Coral/fish tank setup. The Ozone system set up to maintain an ORP of 350. I don't have a problem yet, but I do want to be aware of what to watch for. Thanks for all your help.   Bob Drews <Livestock appearance, reality is the best, first real warning of any such impending trouble... always pay close attention to more sensitive animals when passing by your system/s. Bob Fenner>

Faulty ORP Readings/Copperband for Aiptasia Control - 10/31/06 Hello, and thank you for all the information you provide. <<Howdy, and you're quite welcome...is a synergetic effort>> I have a 125 gallon saltwater reef tank and I am trying to get the Aiptasia under control as well as increase the quality of life for the species I already have.  From my research, I felt that I would try the peppermint shrimp as a way to get the Aiptasia under control and also look at why I have them. <<Mmm...peppermint shrimp are less than reliable controls for Aiptasia anemones, and best utilized 'en masse' re which then leaves you with the problem of what to do with all the shrimp once they've completed their intended purpose...not to mention the expense of obtaining several dozen peppermint shrimp>> I read that the 6-line wrasse could eat them so I moved the wrasse to a fish only tank where he is doing fine.  The next day all 3 peppermint shrimp were gone. <<Hmm...though I doubt three shrimp would have had much impact...at least not for a very long while (assuming they would eat the anemones to begin with)>> I watched my Sailfin tang and it did not seem interested in them.  I only have fire fish, clowns, and an algae eating goby type fish. <<Mmm...how large is this 'goby?'>> With this trail ending in failure, I would like to try a Copperband butterfly. <<Not easily kept...and also no guarantee it will take to the Aiptasia any better than peppermint shrimp>> I read that they are difficult to keep. <<Ah yes>> I want to make sure that my tank conditions are up to standard before I purchase one.  I use the AquaController Pro to monitor the conductivity, pH, ORP, and temp.  The temperature ranges from 74-78 degrees.  The pH is at 8.28 but does fluctuate from 7.99 to 8.28 within a 24 hour period.  The ORP is the strange reading because I show 572 through 678 in a 24 hour period. <<I think this is likely not an accurate reading.  ORP readings this high would certainly have a deleterious affect on your system>> I test for nitrite, nitrate, and ammonia and they always test at or 0 or very close to the lowest scale on the chart. <<Ammonia/nitrite should 'always' be 'zero'.  Do make sure you have fresh/reliable test kits>> I took a water sample to the fish store and he confirmed my readings.  He also tested for phosphate and said it was minimal. <<Whatever his definition of 'minimal' is...>> The alkalinity was acceptable but the calcium was low.  I tested the ORP in my filtered tap water through the Kold-Ster-il unit and the ORP showed 100.  I tested the ORP of the tap water with the salt in a bucket and when agitated with the power head would reach up to 180.  I tested the ORP in my fish only tank and it reads 174.  I do not use ozone at all.  I add the alkalinity supplement every other day and then the calcium supplement on the opposite days of the alkalinity supplement.  I contacted Neptune systems and he said the probe and controller are probably correct and working as they should. <<I disagree...an ORP reading of 678 in your reef tank would definitely be mal-affecting your livestock.  Anything over about 450 starts to become dangerous to your tank inhabitants.  You need to obtain a calibration solution and check the probe's accuracy yourself>> I use a sump with an AquaC 180 protein skimmer and this works well. <<A good skimmer line>> I tested the returns and the water flow is 600 gallons per hour.  I do get some green algae growth in the tank but only enough to clean off of the front glass every few days.  What could cause the ORP to be so elevated without adding ozone? <<Ozone injection is not the only way to raise ORP (increased water flow or adding 'oxidizers' such as iodine can raise ORP levels), but I think in this instance the culprit is a faulty ORP meter/probe>> Do you think the water quality is acceptable for a Copperband butterfly with the ORP reading so high? <<I don't think the ORP is an issue, as I don't think the reading is accurate/that there is any hazard if you are not injecting ozone in this system.  But being successful with the Copperband involves more than good water quality.  You need to have adequate live rock in a 'mature' system (preferably augmented with a vegetable refugium) to provide grazing/browsing opportunities for the butterfly.  You also need to find a healthy specimen that is feeding on frozen foods as getting them to eat is a common problem. Once you have an 'eating' fish, pay attention that it gets its share. These fish are designed for/adapted to browsing the reef for food and don't compete well with most other fishes when the hobbyist dumps in a meal...they even have trouble seeing/finding foods that are swept along in the current.  Most will eventually learn that they need to 'be on the ball' at feeding time, but they will still have problems with the quicker and more agile fishes beating them to the food>> Before purchasing a Copperband, like my other fish, I will find one that has been in the store for at least 2 weeks and that is feeding. <<It will behoove you to set up a quarantine tank for this (all) fish to ensure that it is still feeding (without competition) once you bring it home.  I have witnessed on more than one occasion where this fish stopped feeding after the stress of capture/relocation from the LFS>> Thank you everyone for the time you dedicate to helping me as well as many others. Darrell <<Is our pleasure to assist.  EricR>>

ORP  - 2/4/2006 I recently purchased an American Marine ORP controller. The unit has been correctly calibrated with 400 ORP fluid. I also have an American Marine PH monitor. Both probes are placed in my sump, and been running now for two weeks, in the same compartment as my return pump. Without the use of ozone i am only obtaining a ORP reading of around 220 max. <Not atypical> Tank volume around 970 L including sump. Have 3 fish in the tank 1 Sohal Tang, 1 Naso Tang, 1 small King Angel. Lots of flow in tank using a  Tunze TS-24 kit. Protein skimmer is a Aqua-Medic Multi SL 1000. <Nice gear> I have just ordered  a Deltec Turbo 1250 to sit next to the Multi SL, in the sump. Today i performed a partial water change, and ORP reading has not changed. <Unusual... much volume change? Whose salt mix?> The water is very clear in appearance. I have obtained the following readings Ammonia 0, Nitrate 0, Nitrite 0.3 mg/l, Temp 27c, PH 8.15, Alk 180 ppm, Salinity 1.019. Any advise would be most welcome. Regards Alan <I'd be checking, recalibrating your probe... testing the effluent from the ozone source to see if it's working... Bob Fenner>

Re: Low ORP   2/14/06 Thanks for the information provided, i have tried sending a reply, and received no answer. I am using Reef Crystal salt, and made a water change of around 100 L. The probe has been again calibrated using Pin Point 400 fluid, still same ORP reading of around 210-220. Please note i have crushed coral as a base that has never been vacuumed, and is more than 1" in depth. Before i pull out the sump and remove the present wet and dry, i would like your opinion on the following changes to increase performance. 1. Purchase a gravel cleaner and reduce the gravel to around 3/4 " <A good idea> 2. Purchase a Deltec AP-701 skimmer which is good for 1500L. Because of the media in the first chamber, the supply to skimmer would need to be when the water has entered chamber two. I am not sure if i will be doing this excellent skimmer justice, due to not receiving raw water. <A very good idea> 3. As i have no high flow area in the sump for chemical filtration, i will purchase a canister filter and fill with poly filter and Chemi-pure between. Inlet and outlet same chamber as return pump. <An excellent addition> Please advise if the above is in order, and also any other recommendations to improve my water quality. <... I would also check your effluent water from your ozone source (if this is what you're using to increase Redox potential)... Is it working? There should be a discernible shift in pH, dissolved oxygen, ReDox potential... Bob Fenner> Cukes (comp.) and ORP  9/6/06 Bob, <Scott> The ORP in my 1300g tank is now hitting 500 at its peak in the night. <Mmm... too high...> All fish, corals and other inverts seem unaffected, if not ridiculously healthy.  Should I be concerned or tanking any sort of action to lower it?  I'm not running ozone. <... odd... I'd "check your checker" here first... Likely this is off> Also I was wondering if in your opinion (or experience) an Australian Sea Apple would be capable of catastrophically polluting that volume of water if it died.  Thanks! <Oh yes... Have seen these take out entire stores (thousands of gallons) on collectively plumbed holding systems. Bob Fenner> Scott

High ORP Levels  - 09/07/06 Hi Guys, <Hello Scott> I'm worried about my high ORP levels.  Here is a breakdown of my multi-tank system: 375 liter main tank, 220l frag tank, 300l refugium w/ DSB & Chaeto (reverse daylight photoperiod) & 90l sump.  Lighting consists of 150W 10,000K DE MH's and T5's.  Circulation is moderate to strong provided by SEIO & Tunze Stream Pumps.  Other equipment consists of a Skimmer (AquaC EV-240), Calcium Reactor, Kalkwasser Reactor & Chiller.  Livestock are mainly SPS's & Clams with some fish.  The tank has been running for only 10 months but was an upgrade form a smaller system.  Here are my tank parameters:             pH        -           8.23 to 8.33             Temp    -           26-27 Deg C             Alk       -           9dKH             Ca        -           380 The tank's inhabitants are doing well.  I've recently been dosing ozone with a 300mg/h ozone generator hooked up to an air dryer & controller.  The ozone is pumped through my skimmer in the sump.  I continuously run 800ml carbon split into 4 mesh bags running along the whole length of my first sump baffle which is just after my skimmer compartment.  I normally change 1/4 of the carbon every week when I do my weekly 60 liter water changes. When I first got my equipment to dose ozone I wanted to target a level of about 375 to start off with and then take things from there.  I monitored my ozone for over a month before trying to dose and found that at times my levels would peak at 375.  So I figured that with my levels being what they were I should rather target around 425.  I rigged up the ozone and adjusted the controller to switch off the ozone generator at 430.  My ORP levels did hit the 430 mark about 3 weeks ago.  Just to be safe I unplugged the ozone generator.  The problem is that since then my ORP levels have been rising steadily.  This morning I found my ozone peaked at 456 before lights on. The only time I find my ORP levels drop, other than the usual slight drop during the day, is when I do a water change but it comes back to it's original levels and then some in just over 2 days. I'm starting to get pretty worried.  I hope you guys can point me in the right direction. <Scott, I think the first thing I would do is clean the probe, then check the ORP.  If still high, try recalibrating the unit.  Be sure the probe is not placed near air bubbles and powerheads.  The inductive field near powerheads may affect the reading.  James (Salty Dog)> Thanks <You're welcome.  James (Salty Dog)> Scott ORP Controller Question I have a Tunze 3115 Protein Skimmer which has a port for OZONE. I just picked up a Coralife electronic ozonizer model 100 and a Coralife ORP controller.  <nice collection of hardware there!> My question is: There seems to be a way to check your ORP level when you turn the dial on the controller. But will the controller shut the ozonizer off when it reaches the set point on the dial.  <exactly!> There is an outlet on the unit for the ozonizer. I have check the Coralife website and can't find the answer. So again I come to you for HELP. Many Thanks! John <its really that simple, John. Program a targeted set point and ozone will be injected until that point is reached. Don't aim too high... around 400mv would be fine. And make sure all effluent water passes over carbon. Best regards, Anthony>

Ozone Question Hello Again, I have another question about running OZONE in my tank. I have a Tunze 3115 skimmer, Clearwater Tech Ozonizer, Coralife Controller with probe. I have switched between a few size air pumps. As soon as I turn on the system the skimmer stops producing. Bigger the air pump worse the skimmer works. <it sounds like you are blasting air into the venturi causing large bubbles which reduce efficacy. Supported by the fact that a bigger pump yields worse performance. It is a sucking venturi (!) and should need little or no air flow to draw ozone into the unit. Again... forced air disturbs foam production> I thought the skimmer was going to work better.  <absolutely> Right now I am using a Rena model 100 air pump. It's pretty small.  <hook it up to a gang valve and bleed it lower to see if that helps> Also how long does it take for the ORP level to rise?  <hours/overnight> It has been running for a day and there is very little change in the ORP level. I also do get a smell of ozone in the room. <good heavens! Stop. Do you have a carbon satchel atop the skimmer and pass all effluent water over carbon without any possibility of a bypass? If not you will eventually and literally burn the eyes and gills out of your fishes in days/weeks from the residual ozone in the water and if enough gets into the air you'll start to get headaches as well. Please read the instructions my friend! Ozone is a tremendous benefit when properly applied but quite dangerous if misapplied (like iodine, Kalkwasser or most anything else in excess). Your skimmer needs to be in a skimmer box with a drilled overflow that passes entirely over carbon...not simply in the sump or main display. It needs to be so even without using ozone to have a very static water level for optimal performance. Otherwise they will only work if you top off evaporation at least once daily for consistent head against the skimmer. Best regards, Anthony> Any help would be greatly appreciated. Thanks Again, John

- Ozone Questions - Dear WWM Crew, <Hello, JasonC here...> This is Howard in Wisconsin again looking forward to the new book and once again trying to learn a bit more of what I don't know about this hobby With a two year old set up circulating about 160+ gallons, net - set up and modified 100% in accordance with TCMA and WWM and never a disease process, I should be satisfied. However, several months ago I added a second refugium with "non-Caulerpa" macro algae, peppermint shrimp, worms, copepods, and amphipods. First refugium has 6 inches of fine sand and is packed with often harvested Caulerpa. Fish bioload is about half the "rule of thumb" level but I know that the large 'convicts' living under the rock and sand in caves have created a space that can't be cleaned and gets little circulation. Deep sand (5 inches oolitic), inoculations from 3 sources, and fully cured live rock completed the second refugium which I hoped would be the last step in my little ecosystem. I figured  I could grow natural food and perhaps enough other macro algae to later swap out the Caulerpa in the first refugium. Well, the live sand brought with is a plague of red algae which slowly killed off the 4 species of macros and infected everything else in the system. A very productive Turboflotor, lots of carbon, poly filter, 1600 gph circulation, and my "only when needed" 25 micron - 700 gph mechanical filter all proved inadequate. Frequent chemistry checks continued to show 0 ammonia, nitrate, and silicate (I have R/O and D/I). Nitrates ranged from 0 to 0.4. I used two different low range test kits  to confirm nitrate. I just couldn't figure out what was feeding the red algae! Last week, after reading tons of advice from the web and re-reading sections of TCMA I decided to add the only bit of technology in that book that I did not have - an ozone generator and ORP monitor. This is an addition that I know Bob is very high on but I thought I could do without. The ORP monitor read 60, yes SIXTY while chemical tests still showed no chemical pollution. How is that possible?? An ORP test solution standardized at 200 - 250 mv read 205 so I assume the actual reading may have been even less than 60! How is it possible to have so much dissolved organics and/or low oxygen and still be shown that all is well by the chemistry panel? <You should pose this question to the manufacturer.> By the way, my fish and corals have been fine through all this but now that the ozone has produced a steady ORP reading of about 350 the red stuff is fading. I didn't think my water could get any clearer but it has. If you're there, Bob, thanks again for the ORP/ozone advice. Now I have it all. <<Heeeeee! RMF> I'll be starting over with the new refugium concentrating on Anthony's "non-Caulerpas". I'll wait for the new book and follow you guys' advice on doing so.   There is a mass of tiny bubbles on the walls of the tanks which I hope will subside? I didn't have those with the Turboflotor breathing air only. Are there any creatures or plants that may not like the 350 mv ORP? <Not that I can think of.> The Red Sea generator/controller lets me set it anywhere I wish + or - 5 mv, ozone per hour up to 200 mg. (I'm running 150)With a carbon pad on top of the Turboflotor and a bag in the discharge there is no ozone smell at all. Howard <Cheers, J -- >

New plankton refugium/red algae/ozone Dear WWM Crew, This is Howard in Wisconsin again looking forward to the new book and once again trying to learn a bit more of what I don't know about this hobby <Me too!> With a two year old set up circulating about 160+ gallons, net - set up and modified 100% in accordance with TCMA and WWM and never a disease process, I should be satisfied. However, several months ago I added a second refugium with "non-Caulerpa" macro algae, peppermint shrimp, worms, copepods, and amphipods. <Okay> First refugium has 6 inches of fine sand and is packed with often harvested Caulerpa. Fish bioload is about half the "rule of thumb" level but I know that the large 'convicts' living under the rock and sand in caves have created a space that can't be cleaned and gets little circulation. <Yes> Deep sand (5 inches oolitic), inoculations from 3 sources, and fully cured live rock completed the second refugium which I hoped would be the last step in my little ecosystem. I figured  I could grow natural food and perhaps enough other macro algae to later swap out the Caulerpa in the first refugium. <Sounds good> Well, the live sand brought with is a plague of red algae which slowly killed off the 4 species of macros and infected everything else in the system. A very productive Turboflotor, lots of carbon, poly filter, 1600 gph circulation, and my "only when needed" 25 micron - 700 gph mechanical filter all proved inadequate. <Thank goodness> Frequent chemistry checks continued to show 0 ammonia, nitrate, and silicate (I have R/O and D/I). Nitrates ranged from 0 to 0.4. I used two different low range test kits  to confirm nitrate. I just couldn't figure out what was feeding the red algae! <... could be a few sources> Last week, after reading tons of advice from the web and re-reading sections of TCMA I decided to add the only bit of technology in that book that I did not have - an ozone generator and ORP monitor. This is an addition that I know Bob is very high on but I thought I could do without. <You could> The ORP monitor read 60, yes SIXTY while chemical tests still showed no chemical pollution. How is that possible?? An ORP test solution standardized at 200 - 250 mv read 205 so I assume the actual reading may have been even less than 60! How is it possible to have so much dissolved organics and/or low oxygen and still be shown that all is well by the chemistry panel? <It is likely the dissolved organics are at the base of the low ORP> By the way, my fish and corals have been fine through all this but now that the ozone has produced a steady ORP reading of about 350 the red stuff is fading. I didn't think my water could get any clearer but it has. <Great> If your there, Bob, thanks again for the ORP/ozone advice. Now I have it all. <We'll see...> I'll be starting over with the new refugium concentrating on Anthony's "non-Caulerpas". I'll wait for the new book and follow you guys' advice on doing so. <You'll really enjoy the algae section... the book could be labeled "Marine Refugiums and reef invertebrates..."> There is a mass of tiny bubbles on the walls of the tanks which I hope will subside? <Me too> I didn't have those with the Turboflotor breathing air only. Are there any creatures or plants that may not like the 350 mv ORP? <None that you'll likely want to keep> The Red Sea generator/controller lets me set it anywhere I wish + or - 5 mv, ozone per hour up to 200 mg. (I'm running 150)With a carbon pad on top of the Turboflotor and a bag in the discharge there is no ozone smell at all. <Shouldn't be. Thanks for writing. Bob Fenner> Howard

New reef set-up questions - OZONE usage 7/4/03 Hi Anthony! <Cheers to Greece.> Since my Remora skimmer is not designed to work with ozone , I have decided to start my reef without ozone. Have you seen reefs being successful without the use of ozone? <More often than not, yes.> In case I do not use ozone, is it worth to buy an ORP monitor? <Yes! very much so... and excellent measure of water quality in general.> From the reading I have made so far, it seems that it is a good tool to check every moment your system's overall well-being, and take the appropriate actions when something seems to go wrong. <Quite correct.> My heater is not 200W, as I wrote in my previous memo, it is 150 W. I am thinking of buying an extra heater of 100 Watts and place them both in the sump. <Very wise.> Will the total 350 Watts  be enough for the 270+70 liters of my tank + sump? <Hard to say... depends on the interior ambient temperature and any fluctuations... but I suspect it will indeed be enough.> Best regards, Thanassis  <Kindly, Anthony>

Ozone and Alkalinity Question - 8/10/03 Dear WWM crew, <howdy> My 240 gallon tank is currently running at 375 mv to 398 mv without my Clearwater ozone generator turned on (last several days).   <very fine> The ozone is set to turn on at 345 mv.   <And your hi-point is set for just under 400 I presume?> If I understand it from Bob's book, that over 400 mv is dangerous to the life in my tank. <rather... it's the high end of the safe zone. Agreed> My tests for alkalinity yield 14.0 dKH.  My calcium is 350.  Any advice or suggestions? <your ALK is too high... do let that stray down to a ceiling of 12dKH. The calcium is fine however. No need to fixate on specific numbers... just stay stably within a range> Current parameters: Ph ranges from 8.28 in the a.m. to 8.4 in the p.m. Calcium Reactor effluent Ph is 6.78 Ammonia=0 Nitrites=0 Nitrates=25 Salinity=1.026 Temperature=80 (temperature is controlled) 300 lbs live rock in display, small amount of live rock in refugium.  Live rock teaming with copepods and amphipods. Several white Syconoid sponges present on the rock. Small amount of coral gravel (1 to 2") in display and refugium. Good amount of macro algae in refugium. (Light on 24/7) <all fine> Fish=Picasso trigger (In sump waiting for a home), blue tang, 3 yellow tangs,6 blue/green Chromis, 6 line wrasse, watchman goby, green mandarin and scooter blenny. Corals=torch coral, brain coral, cabbage coral, colt coral, Kenya tree coral, button polyps. Inverts=Crocea clam, bubble tip anemone, cleaner shrimp, coral banded shrimp, tube anemone (in refugium), several hermits and a few snails. <dreadful to see the anemone mixed in with sessile cnidarians/corals... do reconsider removing to a species tank or ancillary tank at least (very risky long-term as a motile cnidarians... unnatural too)> Additional equipment=Acrylic tank with corner overflows, 3-175 w 10k M.H. w 2 - 95w blue actinic VHO's, CS8-4 Euro reef skimmer, 4 maxi jet 1200 powerheads in display tank and 2 Mag 1200 return pumps. <you have a fine system overall... no worries. Best regards, Anthony>

- Ozone Use - Hi Guys, <Hello.> I am in the process of adding a Red Sea Aquazone 100 (with air drier) to my 350l reef tank; connected directly to the Deltec MCE-600 skimmer venturi. The tank already benefits from a electric Pinpoint pH meter running 24/7, giving me valuable accurate pH information without the hassle of test kits. I have the option of paying £150 more to get the Aquazone Plus with Redox Controller (these things are not cheap in the UK!). <Ouch.> My thinking is the controller is not essential given that I intend running the ozone at modest levels (perhaps 50mg/hr) and can indirectly gauge the ozone level via the pH reading (keeping it less than 8.4); saving me money and the time needed to service the Redox probe. Is this an advisable strategy, or is the Redox Controller really worth the money and maintenance? <You'd need to service the pH probe anyway, and using pH really isn't the optimal way to gauge ORP, but I would be as hesitant as you are just due to the increased cost.> I don't have the benefit of a sump on my system, so any excess ozone will return directly to the tank. Is this something I should worry about? <I wouldn't think so... if dosed at the low levels you say you plan to... ozone is highly reactive, and so it's going to be a challenge to have any excess - the ozone will find something to react with.> Would it be advisable to counteract any remaining ozone by putting activated carbon in the skimmer "out" chamber? <Wouldn't be a bad idea as a safeguard, but again... at such low levels...> If I do use carbon in this way, how often should it be changed? <Bi-weekly.> Thank you very much for your help. I honestly believe I would have long since left the hobby if it was not for the sound advice gained from your site. Andrew <Cheers, J -- >

Placement of probe to measure ORP Bob, <Sean> Thanks for the great information. Been doing quite a bit of reading.  Here's the stats for my tank: 75 Gallon w/5 gallon sump (converted wet/dry) - 2 years old:  pH=8; Ammonia=0; Nitrite=0; Nitrate=2.5 to 5; Temp=77F; dKH=12; Calcium=350  40-50 lbs of live rock; 2 inch deep sandbed; AquaC EV-150 skimmer (Mag 7); Mag 9.5 return pump; Korallin Calc Reactor.  One yellow tang ; mated pair of Maroon Clowns; Brittle Starfish; Anemone.  Christmas present from the wife was a Red Sea Aquazone Plus 100 Ozonizer.  Dropped the probe into the sump a few days after Christmas and initial ORP reading was zero.  Figured that the reading must be wrong, and it would take a while to settle in and temperature correct. <... unless the water was distilled... and not aerated... yes> Next day reading still close to zero (I think it was 10).  Connected the ozone to the intake on the skimmer and turned on the ozone production (initially, I had it set so that it didn't produce any ozone) at 10mg/hour and a few days later it was at 100, now it reads approx 275.  Despite all of this, the tang is happy (brighter than any store tangs that we've ever seen) and the clownfish have continued their regular mating schedule.  The Anemone is happy (puffed and spread). <Sounds good> Question 1: Where should the probe be placed to measure ORP and control the ozonizer? <Mmm, in the main tank somewhere... about mid water down> I've seen different information on where ORP should be measured.  The manual says measure in the tank, I've also read that it should be measured at the output of the skimmer.  My concern is that the initial ORP reading seems so low that I'm wondering if the probe is correct (am having a hard time finding a solution to calibrate the probe with).   <There are no such things as far as I'm aware> Question 2: Is a refugium (and corresponding slow water flow) required for Mangroves? <Slow is better... a couple, three turns per hour> I'd like to add Mangroves (in the hopes of driving Nitrates to zero), but space under the tank is quite limited. <Would not do this "under a tank"... these organisms are tall... Look to other life, likely algae> I was wondering if I could float the mangroves in the sump, but didn't know if it would do any good with a high rate of flow through the sump.  Thanks!  Sean Perry PS> Your book was the first one that we purchased (before buying the aquarium), and it's become severely dog-eared from reading and re-reading the various chapters. <We are more than friends then. I thank you for sharing. Bob Fenner>

- Redox on the Rise - Hey guys- Got a question, I recently (last week) bought and hooked up a Red Sea Aquazone 200mg/hr ozonizer and controller for my 70 gallon reef. I set the Redox controller to 310 @ 30mg/hr. after the ozone level was achieved the red light indicating ozone production went off (as it should), but my ozone has steadily risen since to about Redox of 400 presently. To ensure the ozone is not being delivered, I've even unplugged the air supply for the last 3 days, and its still rising! <To what?> I don't know what to do, is this naturally occurring? <Well... you have to expect that the introduction of ozone is going to impact the reduction/oxidation potential of your tank... these changes would not have been instant but taken some time as you observed. Will the production now turned off, I'm sure the level will fall in time... it's the natural way of things. For certain any ozone you have added has more than likely been 'used up' and there is no continuing issue from the presence of ozone.> Have you ever heard of Redox rising this high on it's own, or have I set off some kind of reaction? <I've heard of this, but only in lab experiments. As for you tank and 'some kind of reaction', there's no way for me to know without extensive chemical analysis of your tank, which isn't really practical. I'd just turn off the ozone production and see what happens... I'd be willing to bet the Redox drops in a couple of days. I would also go through the probe calibration steps again to make certain it is not mis-reading.> I would appreciate your thoughts. Thanks again, Justin <Cheers, J -- > ORP meter placing Hi there crew, I hope you're having a grand time. Don't know what I'd do without you....... Anyway, nuff of that for now. Just a quickie, If you please?.......(and not a word from you Marina!.......ok?) <Yikes...> Seriously though I have taken your advice and bought an ozonizer (Certizon model 200, from Sander) and an ORP meter (not a controller). First question is (yup you probably guessed it) where should I place my probe? .......At the moment I have the probe in the main display and it reads 310 so I could do with a little ozone one thinks? <Okay on both counts> I have the input going to the venturi on my skimmer (no air pump as yet) and the outflow of the skimmer is filtered first through PolyFilter & then though carbon. <All righty> Do I need carbon on the top of my skimmer?.....If so this is a real problem as I only have one inch (shut up Marina ;-)) between the top of my skimmer and the base of the tank cabinet. <No need for the carbon> Oh just for the record My LFS said I ABSOLUTELY MUST feed the ozone in with an airstone even though this is a venturi skimmer (Turboflotor 1000 needle wheel) To your knowledge, is there any reason for doing this? <Nope. You can try it both ways... no detectable difference I'd bet> Anyway, one quickie turned into more then just a quickie, sorry 'bout that folks. <No worries> I was about to quit this hobby after many years but you have breathed new life into me and given me the incentive I need to get my husbandry up to date and turn this awful great tank into something wonderful, and I thank you all for that. Cheers for now. Simon <Breathed new life...? I better go brush my teeth! Bob Fenner>

Ozone and Redox Controller Per your advice in the Conscientious Aquarist I recently purchased a small ozone generator Redox controller combination for my 250 gallon tank. After two days the results are outstanding (I think) with perfect water readings and crystal clear slightly bluish water it looks like you could just walk through it is so clear.  <Wowzah, quite a description> Here is the dilemma. When I first started the controller I had a Redox reading of only 95-100 mv. (Whew, didn't think my water was that bad). After two days on low to mid levels of ozone (5-10 ml per 25 gallon)  <Let's make that milligrams of ozone per...> the water looks great as described above but the Redox reading is only 108-109. I turned the unit up slightly but after another 12 hours only hit the 109 number. I could continue to increase ozone but am reluctant to do so since things look and fish behavior is so good.  <Don't blame you... the livestock is the best, grand arbiter of "how much is enough"> Tried the probe in a slightly aged batch of fresh artificial sea water and could only get a 92-98 reading. Does that seem right for fresh sea water with no organics at all?  <Hmm, no... should be 250-300 plus microSiemens per centimeter... depending on mix, source water...> I am beginning to suspect the probe/controller may not be accurate.  <Me too> I do have some slight residual copper from an earlier treatment but don't know if that would effect it either. <Nah> Have ORP test solution on the way but would sure appreciate your thoughts. <Have your probe probed... check the checker...> Thanks as always <Be chatting. Bob Fenner>

ORP too high? I am a faithful daily reader of this column and I truly appreciate all your excellent advice. My question relates to ORP - specifically if it can be too high. My new tank (not my first) is 180 gallon regular with 220# of M.I. live rock, 125# live sand. This is my equipment list: 2 175W 10,000K Metal Halides, 2 55W PC white, 2 55W PC actinic, 1/3 HP chiller with dedicated Iwaki MD 40RLXT pump (on/off w/ chiller), Iwaki MD70RLT main pump, ETS Gemini 800 Skimmer w/ dedicated Iwaki MD55RLT pump, K2R Calcium reactor. Lately, to avoid overheating/overskimming the tank and save energy costs, I only have the skimmer on for the 12 or so "night" hours. The waste produced by the skimmer seems to be about the right amount, based on my past experience with downdraft skimmers. The ammonia and nitrites are zero, and the nitrates (w/ a reef test kit) are about 3 ppm (correct scale? where <10 is good). I control everything with a Neptune Systems AquaController. When I first set up the tank a month ago, the ORP hovered around 300-350mV. Now the Ca reactor has been going for about two weeks, and my ORP has gradually climbed up to about 425 mV. This may seem silly, but should I worry about the ORP being too high? I do not use ozone. The probe supposedly does not need to be calibrated. I moved the probe around different "sides" upstream/downstream of where the CA reactor doses into the sump and get about the same reading. I don't think the ORP probe (brand new) is too close to either the pH probe or the grounding probe. I run the reactor at 55-65 bubbles per minute, with effluent flow of about 30 ml/min at pH 6.6, all as recommended by the manufacturer. The pH in the tank is rock solid at ~8.2-8.3. Is my ORP really this high? Is this OK? Should I be happy about this? All my fish and all my corals look great, but I just wanted to see what your opinion might be. It just seems weird... >> Hmm, not weird at all, and very beneficial... Yes Oxidation Reduction Potential can indeed be too high... but depending on the actual "cause(s)" anything up to about 500 micro Siemens per centimeter (I think the next change in units ought to be micro-bobs...) is okay... Am a little curious about any measure of biominerals in this system... i.e. you may be a little high on driving the CO2 through your reactor (bubble counters are notoriously "inaccurate", "imprecise"... they just don't give an "average" count that means much at times...).  Anyhow, for our general understanding here... and in perpetuity (love the net!), you're adding charged particles (Ca++ and more) to your system... increasing its conductivity (the indirect way that ORP is measured... right? as in the units it's measured by your meter...), increasing the ORP respectively... Does this make sense? Think back to the James Bond film where he throws an electric fan in a bath tub with the bad guy... Would you rather it was a tub of milk? distilled water? Or your system with the reactor turned up? Take the milk... non conductive, then the distilled. Bob Fenner, who REALLY likes calcium reactors and CO2! 

ORP drop with water changes????? Bob: This has been bothering me for some time, and I can't figure out why it occurs. Every time I make a water change (done with ro or deionized water, mixed and heated properly, allowed to stand 48 hours or more before actual change, 35 gallons changed out of a 180 gallon tank at a time), my ORP reading on my computer plummets a hundred points or so and takes a week or two to improve. Generally coral polyp extension improves immediately, water appears clearer, in other words all visible signs look good. If I have decreased the amount of particulate and dissolved organics in the tank, why would the ORP go down and not up? >> Well, the answer is quite... simple: and with apologies to the folks at Tumwater, "It's the water, and a lot more". Think back to your early chemistry classes. (Geez, I used to teach the physical sciences at the HS level...). Remember that Redox, oxidation-reduction reactions (aka acid-base) are a type that involves the loss or gain of electrons (the ever useful acronym OILRIG, "oxidation is losing, reduction is gaining"... electrons)... Now, when you're changing water a bunch of "things" are happening, but one overall reaction type that registers on your meter... the combination (read that as neutralizing) of existing organic acids in your old water by the mix of mainly alkaline minerals... Ahhh, hence less conductivity, hence lower ORP reading... but as you know, not really an indication of "viability" of your water... A danger of aquarists/humans relying on a point, as a reference... and a useful illustration of the subjectivity of the human experience, eh? A pleasure, as always. Bob Fenner

Question: Hi Bob-I have a 240 gallon set up with a deep (6") sand bed. Circulation is about twenty tank fulls an hour. My trouble is that without ozone I cannot get my Redox readings above 250 mv.-with ozone (Sanders unit set at 200 mg./hr. through venturi in Tunze skimmer) I can reach 370 no problem and everything looks great. However, I am worried that the ozone is depleting some elements and perhaps harming some corals (mostly LPS and soft). Alkalinity is 3.5 mEq/l, SG. 1.026, temp. 79. Few fish, no feeding. Is my sand bed degrading the tank environment with excessive BOD? thanks for your input.

Bob's Answer: Hey Kurt, no real worries with ozone induced readings... The reductive environment in your humongous sand bed NNR is no doubt having an effect, but not one I'd worry about. I would run the ozonizer, and not worry a wit re: Redox effects here. Don't think you have an excessive biological oxygen demand (this would show up in a few ways in your tests and be observable re: your corals...). Do you utilize Ca supplements or CO2? All in all, if "it ain't broke" (and I don't see that it is) I wouldn't fool with it (you may quote me).

EC/TDS Meters Mr. Fenner, I purchased a Milwaukee Model SM301 Conductivity and TDS meter, but found that it has very limited instruction on how to read and define the meter reading. I was wondering if you might have any knowledge of this. The following are some of what I am looking for plus any other info you can offer. <Hmm, would contact the Maker: http://www.miltestersusa.com/  re better, more instructions... and/or the folks who sold you this gear.> Meaning of mS/cm? <micro-Siemens per centimeter... a "new" standard of conductivity measure equivalent to "micro-ohms per centimeter"... the company "Siemens" IS that big, influential"... A higher reading indicates more ionic content, higher conductivity...> The range of the unit is 0 to 1990 mS/cm. What is considered a normal reading? <Normal for what? Marine, brackish, freshwater, koi ponds, water for epiphyllums...? Again, I would, will cc Milwaukee Instruments here... Bob Fenner, WetWebMedia> Leldon

ORP Hi! There, <Hello> I hope all is going well. This time I have a question about ORP. <Okay> I have a fifteen hundred gallon system that has been going for about three months now. I started off with a specific gravity of about 1.018 and then did a 100 gal water change last week. The SG is at 1.0195 now. It seems that the Ph has dropped just a little bit (8.08-8.24) now. Also the temperature dropped a little bit as I moved up my halide lights. <All to be expected> However what is puzzling to me is that my ORP readings are between 390-410. That seems so high. They used to fluctuate between 350-395. Please tell me if my ORP probe has gone bad and I need a new one. <Mmm, you might well want to "test the tester" here. Don't know if the probe is off, or your meter... but would try another tool><<Is/was likely just the boosted photosynthesis-effect. RMF>> I know ORP is connected to a variety of things like Ph, Temperature and many other parameters but I am concerned because of the change. At what point do I start to get worried? <Never worried my friend. Concerned and directed enough to direct your actions toward safeguarding your system and enjoying it. Bob Fenner, who would be concerned if the Redox potential shifted more than ten percent in a given hour to hour in a day frame (let's say Tues. at noon compared with Monday at noon), or if the Redox dropped below 350 or so... definitely would be looking for remedies anywhere near 300...> Thanks again, Bhaskar.

ORP Mystery Hello Bob Fenner and crew. <<Howdy!>>I have a 250 gallon salt water tank which has been in operation some two years now. Great hobby despite the ongoing trials and tribulations but, that is what makes it fun I guess. A voyage of discovery no doubt. The tank is 48" tall 36" wide so I guess it fits the definition of the dreaded show tank. The tank has never run a super high ORP and tended to settle in the high two hundreds (275 or so) even with the addition of a small amount of ozone through the skimmer. About two weeks ago the ORP took a nose dive to 220 or so. Checked circulation. Same as always. No missing headcount which might be a loss fish fouling the system. Further research on ozone systems indicated that the CD tubes that produce the ozone are only good for a year to 18 months. Was using a Red Sea unit rated at .2 grams per hour but usually ran it at .1. Replaced the unit with a Clearwater since it has provision for easy CD tube changes rated at .3 grams per hour and have been running it wide open for about 24 hours now. ORP still stuck at 225 or so. I have tried 3 different ORP probes on two different meters and all confirm the 220 or so ORP reading. Sand is clean and while there is no obvious build up of other material.. Live stock seems to be doing OK but with some labored breathing noticed. Any ideas? Stumped in Vegas <<As you know ORP is only an indicator....I would break out the dreaded test kits and have a full look. There is something wasting or building up somewhere. (that's why you have the ORP to begin with) Start with your make up water and proceed step by step. It doesn't sound like your ozone. Labored breathing would lead me to testing ammonia, nitrite, nitrate, pH, etc. Give this a try and see if you find it. Hope this is it, Craig>>

Follow up, High ORP Guys, as to my question about the high ORP of my reef tank ,450 gal plus 90 gal refugium, not overstocked with fish, not overfeeding. <understood> I thought 350-390 was an ideal range, what range should i be comfortable with a set up like mine, thanks Paul <You are correct, Paul. 350-390mv is a fine range. I take no exception to that (see first message pasted below, "yes... agreed 375mv is quite fine"), but rather.. I am concerned about the statement that your Redox has leveled higher than the setpoint (!) and climbed as high as 432 even with the airstones off and even the skimmer off for 2 days!! That is a problem... its not even possible. You have a malfunction with your Redox meter/probe, my friend... experiment until you determine the cause. Best regards, Anthony> ORP unnaturally high? Faulty meter Guys, my reef setup, 450 gal plus 90 gal refugium is doing fine except for one mystery. I  have been running an Aquazone 200 mg for 2 months and the ORP stabilized at about 375, <holy cow!!!! How much of that 200mg are you running?!?! That is way too much for a tank this size unless you feed very heavily or the tank is overstocked (requiring the heavy ozone). And keep in mind that the mfg telling you what size unit you need is also trying to sell you something ;)> the value i had set the unit for. <yes... agreed 375mv is quite fine> Slowly, even though the unit was not producing ozone, as shown by the ozonizers indicator light, the ORP reading was rising. It is now at 420,but has hit 432. <unless you have an extraordinary skimmer (RK2 or the like) with massive, almost pressurized oxygenation as well as frequent water changes and heavy chemical media... I would doubt this reading. Redox does not climb easily for most any system. Unnatural> I have adjusted the ozonizers settings to minimum, thinking the indicator light malfunctioned, ORP stayed at approx 420,turned of my airstones, no change, even shut off the EuroReef cs12,for a 2 days. <awesome skimmer, but yes... your ORP should have dropped measurably as soon as the skimmer was turned off if nothing else. This unit is misreading for certain> Tank looks great, should i be worried? Thinking the electrode or unit could be faulty. <agreed... or something else. Feeding, lack of skimming and simple time (hours) will bring down the ORP. We have faulty equipment here> I have not changed anything else, same feeding schedule, etc. Thanks for your input, Paul. <best regards, Anthony>  

Redox help Dear Mr. Fenner, My name is John Perry and I have a Redox question that so far I haven't been able to find an answer to.   <Okay.> Last June I setup a new 135 gal overflow system with a big Berlin protein skimmer. In the beginning I had a high Redox value at about 500mv and the local fish guy said that my water was too clean so I should either remove some of my filter media from the sump or put in more fish, I chose to do both. When I did my Redox went down to 350mv so I was very happy.   <High Redox is an indicator of good water quality, why on earth would you be encouraged to lower it, and thus the indication of water quality? Have you searched on Redox (oxidation reduction potential) at WetWebMedia.com? This is the most basic information about Redox, it would be advisable to find out more!> But about a month ago my Redox value started to climb again bit by bit everyday almost. When it got to about 400 mv I turned off my skimmer but its still climbing and today its 490mv.  On the internet the only thing I've been able to find is how to raise the value not lower it so I'm at a loss as to what to do. <This is because higher is better, not the other way around. Do understand, high Redox levels of over 450mv are common in well-oxygenated coral reefs free of nutrients, and less than 200mv in nutrient rich lagoons with lower oxygen saturation. Your skimmer should run 24/7 and a constant Redox level of 350mv or higher is desired. Redox levels are an *indicator* of water quality. Falling Redox indicates a water quality problem, a higher Redox indicates good water quality. You may want to check your pH to make sure your elevated Redox isn't from a depressed pH. You should shoot for a consistent level.  When it starts to fall then it's time for maintenance or to look for reasons for water quality degradation.> Since the setup I've only changed the water twice including yesterday where I changed 15gal and I haven't cleaned out my filter at all. If I clean my filter media will that remove some bacteria therefore reducing the Redox level? Any help you could provide would be GREATLY appreciated. Sincerely, John Perry P.S. I love your book "The Conscientious Marine Aquarist" it has been indispensable and has helped me learn a lot, thank you! <Do read up on Redox potential before worrying about higher levels. You have been mislead by your LFS to think lower levels are desirable, this is not the case. What you want is consistency and no big swings higher or lower. Levels over 350mv are adequate. I suggest getting the pH meter as well.  Best of luck, Craig>

Re: Redox help Thanks a lot for your quick reply, I really appreciate it. I was concerned because in all the information I could find on the net including wetwebmedia.com said that Redox readings over 400mv were dangerous to life I was wondering in what way is it dangerous,  so that's why I was getting worried. I'll go and check my PH maybe it's out of whack. Thanks again for your help. Sincerely, John Perry <Glad to help John!  Let us know how it goes! Craig>

ORP level for controlling Ick?  5/103 Wet Web Media Crew Hello, I have a reef tank 500 Liters, and I'm using Aquazone 100 mg With ORP Controller, What I would like to know - How high should the ORP level be if I would like to Kill \ Weaken the ICK? thanks in advance,    Asaf. <there is no direct/correlative reading of ORP for controlling parasites. Disease control begins with proper quarantine of all new livestock in a separate vessel for 4 weeks prior to entry in the main display. That said... a good Redox value with ozone in the aquarium is around 400mv (350-425mv range). Stability is better than occasional spikes to unrealistic highs (some folks push ORP to 450mv or higher). Best regards, Anthony

Redox Hello everyone! <Thanassis> I had my new 85-gallon reef running only with salt water for some time and the ORP monitor had a reading of 280 to 320. Two days ago I received my first box of live rock from Indonesia (about 45 lbs) and put it in the tank. After I placed it in the tank my Redox has been increasing constantly and today it has a reading of 400 ! I thought that the Redox should drop because the quality of the water is declining due to the slow curing of the live rock. Is this high reading normal ? Best regards, Thanassis <Likely so and nothing to worry about. The reduction oxidation level will slowly begin to drift downward with aging/curing of the live rock. Bob Fenner>

Redox 9/9/03 Hello again! <cheers my friend> My new live rock has cured within 4 days! Ammonia is 0, Nitrite is 0 and nitrate is 5 ppm. I checked it again on day 5 and I had the same readings. Isn't this strange? <somewhat uncommon... but a good sign that your live rock was handled well> I have already read in the FAQ's session that it had happened to somebody else, so I do not worry much... <correct> My Remora skimmer is still producing a lot of dirty stuff. <yes... the more the better. And a very good skimmer too> I put a Polyfilter and some activated carbon in the sump to start collecting the dirt created all these days. Yesterday I put a couple of small hermit crabs just to see if they survive and to check on my Ammonia test and they are doing fine! Does this mean that I can proceed placing the sand and my first clean-up crew? <perhaps... but it would be better to run to at least 2 full weeks to be sure water quality is stable> My Redox is still at 415 (I do not use ozone). Bob has told me that it will drop while the live rock cures/ages. Is it still safe if it stays above 400? <yes... anything under 425 mv is fine> The live rock has 3 to 4 types of Caulerpa on it, which is starting to grow (some of it survived the trip from Indonesia), a couple of sponges and some other creatures that I am not sure if they are Aiptasia to Fan Worms. Is it a good idea to add a Peppermint shrimp soon ?   <not necessary... and they may kill more good things than bad. I'd leave them out> Is there a risk that except from the Aiptasia it will eat other live stock on the rock as well (the fan worms for example, in case they are this). <its more of a concern with them encroaching on other animals and burning them back. do try to chisel the anemones off the rock to be sure they are removed while there are few in number> I am thinking of leaving the tank with no fish for the next 3 weeks, because I suspect that I transferred Oodinium from my quarantine tank to my display tank using the same bucket. Is this long enough? <fairly safe, yes> Can I however put the clean-up crew (snails, brittle star and shrimp) ? Are crustaceans not infected by such illnesses? <not affected... but they can carry it> Sorry for the too many questions. Thanks a lot for the support. Thanassis <best regards, Anthony>

Low ORP in new tank 10/13/04 Two weeks ago I filled my brand-new reef system with 2100 liters of RO water and mixed in Kent sea salt. I have had the system running since then with a 12 x p/h turnover, no livestock, no decoration and no filtration media other than filter floss so the water should be free from organic materials, pollutants and well aerated. Yesterday I added an ORP controller to the system and it reads 85mv. I would have expected it to be much higher. Is it normal to have such a low Redox potential in practically sterile water or should I be looking for a pollution source / ORP controller defect? Thanks, Timon <the reading is not correct... all ORP probes need several days to break in (do re-read instructions for reassurance of this). You can expect a reading of 300-350 Mv likely. Do recalibrate the probe if a "normal" reading does not show after several days. Anthony> Water Changes & ORP To WWM Crew - This is an amazing site.  Thanks for all the wonderful and free advice.   <always welcome my friend> My question is:  twice a week I make water changes on my 125 gallon salt tank (1 ten gallon change on Wednesday and 1 five gallon change on Sunday) using buffered DI water that has aged 4 days.  Every single time I do this my ORP immediately (within minutes) drops almost exactly 150 points from 370-380 to 220-230.  This happens with both the five and ten gallon water changes.   <this is quite normal... it should recover within 24 hours> The ORP probe is at the opposite end of the tank from the sump return in which I add the new water - so it makes the rapid change even more puzzling.  The ORP gradually returns to normal over the next 24-36 hours.  The only creature bothered by this is of course me.  It doesn't seem to make any sense.   <understood... but it is normal/natural. The new water has not been exposed to great surface areas (turned over in low long tank) nor vigorously aerated as with a skimmer... and add to that the water change stirring up sediments that lower ORP, etc> Just to satisfy my curiosity - what is the mechanism or chemical reaction that causes this?  (I just bought an ORP probe a couple of months back and am no longer blissfully ignorant of the variations in ORP.)  Thanks! Scott <good thinking/curiosity... but no worries. Kudos. Anthony>

High ORP Readings I've read a lot on your site and I find it wonderful!  In fact, this is the second time I've requested help from you.   <welcome back :)> I now have a question about my aqua controller's ORP reading.  It's been operating on my reef for about a month.  I had to send it back about two weeks ago for some repairs in the logging portion but overall it's been great!   <agreed... ORP meters are a delightful means of monitoring water quality. Do not be concerned about the exact number per se (have a wide rage like 300-400mv), but instead use it as a tool to observe changes and shifts caused by changes in the aquarium (water changes or lack thereof, food types, etc)> When I first set it up, the ORP reading was showing in the low 100's and slowly, about 25-40 mV a day, it began to increase.   <this was an adjustment process... your actual ORP was never below 200 mv I assure you> I add phytoplankton and Reef Solution about every other day and that would always cause the ORP reading to drop on average 100-150 mV but after a few hours, recover.   <yes... exactly my point above. It help you to tune your handling of the system/husbandry. Do reconsider too if you actually have creatures in the aquarium that eat phyto (gorgonians, bivalves?)> I also add two part calcium as needed by calcium testing or about every third day.  When it finally reached 350 after about a week I felt no worries.  However, it continued to climb and now it is averaging about 500!   <not likely/possible without the use of ozone. A miscalibration> It still drops to about 350 when I add the additives but shortly recovers back up to this high ORP reading.  I calibrated the pH meter today and it is temperature compensated (Temp is calibrated as well).  ORP reading is pH compensated too so everything should be working right. pH varies between 8.3 and 8.1 day and night.  Temp is averaging between 77F and 79F - I haven't hooked these to the controller yet but eventually plan to.  It's been reading between 480 and 510 for the past week or so now. <again... not possible unless you are pumping a staggering amount of ozone into the system> I am concerned because I've read on your Redox page that anything over 400 can be lethal!   <Hmmm... rather subjective. For hardcore reef aquariums, even 425mv is quite safe IMO... although indeed on the precariously high end> However, nothing in my tank appears to be dying or being harmed; in fact it my corals are still growing like crazy.  Frogspawn, Torch are all splitting, Pulsing Xenia is growing taller and wider.  Other corals are doing well.  Fish include a pink spotted shrimp goby, purple Firefish, gold banded maroon clown, purple tang, & a mandarin fish.  I also have an arrow crab, peppermint shrimp, some scarlet hermits and some blue legged hermits and one sand sifting star.  I have a lot of those 3mm light grey looking two-four legged starfish all over. I have a 50 gal reef set up for over two years Four 55W 50/50 Comp Fluorescent lights ~90 lb live rock ~100 lb sand SOS overflow to sump with aeration drip plate and no bio-balls (water just streams into the sump and aerates very well) Heater in sump Sump Pumps to a chiller then back into tank via submerged ~1' multi-ported header pipe.   I have two Zoo-Med power sweeps in each corner of the tank for circulation and mild mechanical filtration with the suction sponge. The Neptune System instruction book says ORP should never need to be calibrated.  What do you think? <I disagree... no calibration is ridiculous. Although, I also admit that accuracy (calib) is not as important as precision (ability to measure change regardless of start and end points). No worries... the ORP meter is simply a tool for measuring changes and trends. The observation of a food causing a (for example) 40mv drop is far more useful than a questionable day-time high of 510 mv. Just monitor trends my friend and fear not unless you wish to harness ozone (in which case you need accuracy and precision). Anthony> Chris Bovia

High ORP? 10/27/04 Hi Crew <howdy> I have a 120 Gallon Reef tank that has an ORP reading of 395 mV in the morning and 380 at night. <very fine/normal> I'm confident that the readings are correct because I checked the probe and meter with VitalSine ORP cal solutions of 240 mV and 470mV. In each case the meter reads within 4 mV of the test solution. I am not using ozone. PH is 8 .2, temp 79 Degrees F., Ammonia, nitrites, nitrates = 0. These high ORP readings please me and make me nervous at the same time. <huh? not clear on the interpretation of them as "high". These are quite normal in healthy tanks. Ozone can and will push them over 400mv... but this is not needed> I've read time and time again that readings above 375 mV are dangerous. <hmmm... I disagree here, or rather will state that over 425 is> Is a high ORP (>375 mV) dangerous if it occurs "naturally" i.e.: without ozone? <it is not dangerously high my friend... you likely have some/all of the following: heavy aeration, strong skimming, light bio-load and a good feeding/water change schedule. Best regards, Anthony>

Ozone reactions Hi guys (Any girls?) <Yes, there are a few> I do not know if you remember, but I sent a message some months ago about setting up a marine system in Shanghai China. Well, to update you if you do, its been about 6 months now and everything seems to have settled down quite well now and the tank looks great. However, whilst back home in the UK over Xmas I brought a C100 Certizon ozonizer and ORP monitor. On return to Shanghai linked it all up and began slowly to add ozone to the system, its now fully cranked open after 4 weeks and am maintaining a level of 350. The water looks crystal, and most of the occupants seem to have adjusted to the water now, except my sea apple which has not shown its tentacles for about a week now, and the tube anemone which is only partially coming out of its tube. Is there a reason for this reluctance to emerge due to ozone and therefore drop the monitor level, or should I just wait longer to see what happens?  <Dave, in my opinion and ORP of 350 is a little high, especially since you don't mention filtering the return water with carbon. I would run this at about 300. James (Salty Dog)>

Ozone reactions Hi James (Crew and Girls Oops!!!), Thanks for the quick reply, but am a little confused as most of the reference books and generally on your site a recommendation of between 350 and 400 is normally stated as the target, and above this can be dangerous. <You may have misunderstood. I didn't know you were filtering the ozonized water with carbon, this is essential. Then, if you want to keep it at 350 ORP is up to you.>  For reference I have a 180G system with mainly sot corals, some live rock (difficult to get good here) and inverts. Fish= yellow tang, Dottyback, blenny, goby, clown, Chromis. Mainly small fish except the tang. My system being Chinese design is not the best, but consists of overflow box containing bio balls filtered before and after then into a 4 stage sump. Stage 1 now fitted with large Chinese skimmer, stage 2 & 3 coral stone and stage 4 fitted with internal pumps and heaters and a second small skimmer. I have placed carbon between 1st and 2nd stages of sump. Also fitted is ½ hp chiller and a small 9w UV (Fitted before ozone system on advice of Chinese shop keeper, hmm), and now an ozone monitor controller. I also noticed since the introduction of the ozone that the large skimmer in stage 1 has produced nothing for about 4 weeks now, but before the ozone was producing about a cup a week or so. <Yes, the ozone is oxidizing the organics so you would see a reduction in waste.>  So my question would be: 1. 300 ORP reading after other readings, site seem to imply a higher level of 350-400. 2. The use of carbon in a mainly coral, invert system  <With ozone, outside of filtering the ozonized water with carbon to remove any residual ozone, is not really necessary.> 3. Due to the ozone going through the skimmer in stage 1 of the 4 stage sump, is the carbon on the outlet necessary? <As long as the ozonized water is going through carbon. Personally, I prefer Chemi-Pure over the regular carbon.>  Especially as there is some between the 1st and second stages although not perfectly sealed. 4. Should I de-commission the UV? <I don't think this is necessary either with ozone.> 5. Do you know anybody who would ship a clean up crew to China as they just do not do this here  <Probably cost you an arm and a leg for air freight. I'm sure some would ship.> 6. What is the weather like there, as it is very cold and wet in Shanghai? <I'm in Michigan and it's wet and about 30 degrees.> Best regards, Dave   <Good luck. James (Salty Dog)>

Almost murdered by fish with ozone, what now? 5" Sailfin Tang and five small to medium Blue-green Chromis. New ozone generator was running fine, doing what it is supposed to do. Did a water change and turned the system back on including ozone. About 4 hours later, found tang and one Chromis is in very dire straights with the other Chromis looking tired. Hard corals were just starting to show a little stress, but nothing too bad. Shutting down ozone and adding fresh charcoal (the old stuff was only a couple days old) seemed to do the trick, so I'm sure ozone was the problem. Fish came around but tang is still a bit sluggish an hour later. Corals looked fine by then. Total time under stress was about 20 minutes. What do you think the prognosis is for a full recovery? What can I do to help recovery? <Should be fine... if not killed, burned too badly initially> ORP controller was working and only read about 240mV when fish were under stress. I checked with another meter to confirm and it was 260mV (I had just checked both with calibration solution earlier in the day so I am confident in the ORP values). ORP was 375mV before water change. <A big high... starting from?> Guess I learned the hard way that ORP is not an absolute measure of ozone hazard. I started out running Ozotech 250 into skimmer at 50%. ORP seemed to flatten so I kicked it up to 70%. After a day at 70% everything looked great. When I turned the system back on after the 20% water change, ORP was around 160mV. Since 70% seemed fine and ORP was so low, I figured that I could run it at 100% for a little while. Boy was I wrong. <... yes, once the easily oxidized material is gone from the system...> I haven't read much about people using O3 test kits with their ozone generators, usually just ORP controllers. Is it possible to use ozone generators safely with just an ORP controller (plus more patience) and no test kit? <Yes> What's a reasonable starting point for the amount of charcoal and the time between changes? <A few ounces per fifty gallons or so... switched out every few days. Bob Fenner> Regards, George HLLE-And Poor Husbandry-Not Just A Coincidence... 7/22/05 I've read through the facts, and I see that HLLE (head and lateral line erosion) is caused by poor diet, poor water quality, stray voltage.. etc. <Well, it's not 100% certain what it is, but those seem to be the likely culprits!> My question is this. I recently moved from Baton Rouge to Kenner (Louisiana) and I'm sure you will agree with me when I say that usually the local fish stores and the way they do things is generally the way the hobbyists end up doing things in their own aquarium, in that city. (wow did that make sense??) <I think I'm following ya'!> What I mean is that there really is only one prominent shop in B.R., and they rely heavily on hang-on-the-back filtration, really don't utilize ozonizers, use one brand of protein skimmer etc. <I see...While mechanical filter systems have their place, I think it is a bit narrow minded to use only one methodology to the exclusion of all others....Whether it's in Baton Rouge, Boise, Honolulu, or Outer Mongolia! Hobbyists and businesses need to be open to different ideas and accept the way that there is no single best way to do things in this hobby.> And the hobbyists that shop there have tanks that reflect this method. I noticed in a lot of aquariums in Baton Rouge that HLLE was present, but obviously caused by the lack of water quality.  In these cases it was easily reversed. <Very true in most cases, as you correctly observed.> In New Orleans, there are several shops that utilize sumps, ozonizers, and calcium reactors, and the hobbyists out this way are really more in tune with their systems, and water quality. They feed really well, and frequently, and do smaller water changes. <I think that these methods are better long-term solutions for most hobbyists, despite the initial perception among many novice fish keepers and even some (retailers) that they are "more expensive", "more complicated", etc. In the long run, a better system, properly set up for a sustainable population of fishes will save countless dollars and needless fish and invert deaths. This is NOT a cheap hobby, but an initial investment will pay dividends down the line...We're on the same page here, my friend! Off the soapbox for me now!> I'm doing maintenance and have noticed, oddly enough, that even though the water quality is drastically better, and fish are getting a better diet and (theoretically) they should have no HLLE....but it is a prominent issue that I'm dealing with. I'm talking sever cases, and not just on tangs. And the only thing these customers of mine have in common is that they all have ozonizers. And the ones that don't, do not have HLLE. <Well, in the absence of other filtration adjuncts and means to improve water quality, ozone would have a much greater impact. It is an extremely valuable ally in the maintenance of healthy systems, if properly applied. Good observation by you.> I'm about to start treating with Zoe and Zoecon, (have had remarkable success with these products in the past) and my question to you is should I experiment with cutting down on the ozone? Placing it on a timer? How long should the ozone run to be effective? They are currently on 24 hours a day. <Well, I don't think that you need to run high levels of ozone, but you do want to check overall water quality parameters (such as nitrate, which is a great "yardstick" for measuring overall water quality), and it may be applicable to use a Redox controller to monitor ORP if you are a serious user of ozone...although that might be a bit over-the-top for many hobbyists, IMO. I think that, in the end- common sense stocking and overall good husbandry-including the use of ozone, if you feel it is warranted, is the best solution. Additives such as Zoe, Selcon, etc. are always nice to enhance the nutritional value of prepared foods. Also, menu items as simple as fresh macroalgae, such as Gracilaria, do wonders for many herbivorous Tangs and Rabbitfishes (which are notoriously susceptible to HLLE). You sound like you've got a great understanding of the problems and methods to address them!> Is the HLLE and the ozone just an odd coincidence? <I don't think so. The connection between the high water quality that ozone (or other good husbandry habits) affords is no coincidence, IMO. Hobbyists who use care in stocking, maintenance and overall husbandry seem to have a much lower occurrence rate of such problems, in my experience. Keep doing what you are doing, and preach the benefits of good husbandry and observation to your friends!> Thanks (again) for your guidance, Niki -Coral Connection <It was nice to hear from you, Niki! sounds like you've got it down good! BTW, for more on the HLLE condition and some good treatment ideas, do check out a recent article by good friend and WWM/"Conscientious Aquarist" on line magazine contributor Steven Pro on this very topic in "Reefkeeping" on line magazine. A very good, nuts-and-bolts analysis of this condition. Best of luck to you! Regards, Scott F.>

HLLE...(Cont'd.) 7/27/05 Hi again Scott, <Hi there! Sorry for the delay in getting back to you!> Terribly sorry to bug you, but I don't think I quite understood the answer. Would you say that the ozone might be lending a hand in the fish becoming heavily afflicted with HLLE? <No, I don't think it is...I do think that if applied correctly, ozone can be a great assist in maintaining a cleaner environment, thus reducing the potential for diseases and maladies such as HLLE> It seems that even though I treat with food supplements, and increase water change  (smaller more frequent) that the HLLE does not go away. (As it does with tanks that have no ozone) The only correlation that I see between the tanks that have the HLLE that is not reversible is that the ozone is on 24 hours a day.  Best regards, Niki@Coral Connection <Well, Niki- I've never seen or heard of ozone as being a contributor to more serious HLLE condition. On the other hand, there is not a whole lot known about the real causes and "cures" for the condition in question. Much of what we "know" about HLLE is from anecdotal observations, etc. It's important to follow up on your theory/observation. Why not try reducing the period of time when you dose ozone, or even eliminating it entirely? Since you're basically testing a hypothesis, it's worth a try! Maybe there is a correlation in your case...Good luck! Regards, Scott F.> Ozonizers, proper levels 7/26/05 Dear Crew, I've read about ozonizers on WWM, and wish to elicit your educated opinion: Approximately how many milligrams of ozone er hour -- per gallon of water, and injected continuously -- is both sufficient to be effective, as well as safe to inject without any kind of ORP testing protocol? This probably varies slightly based on bioload, so lets be conservative. <This is the problem, Joe.  Bioload.   It is difficult to suggest milligrams per hour of ozone, too many variables, including bioload.  To be safe, I would get an ozone generator with controller and set the ORP level at 325.  James (Salty Dog)> Joe Kraska San Diego CA USA p.s. backyard renovation continues; pond digging soon... :)

Ozonizer 7/29/05 Hi!  Hope all of you are well!  I have set up an ozonizer (the one I could afford).... Red Sea brand.  Hooked it up as this:  An air pump that hooks up to a dryer.  Air in, air out.  Air out of dryer goes to ozonizer and then from ozonizer to venturi port of skimmer.  However, my skimmer is going nuts!  I am now just collecting at best, tinted water.  What to do? <Mmm, try adjusting the inflow of air, ozone... you may not actually need the air pump at all... but just a check valve twixt the skimmer and ozonizer (lest power go out, to prevent capillation...> (It is a Turboflotor).  My set-up has been explained to you all so many times that I wish I could just cut and paste some saved version of it in!  All parameters looked good.  Salt 1.025, nitrite and ammonia 0, nitrate 10ppm, KH about 12 and Ca 300ppm.  PH runs about 8.1 to 8.4.  (night/day).  Even have an oxygen test that said 7mg.  I change and clean things once a week with 20 gallons being exchanged.  I wish I could only do a 10 gallon water change, that salt gets expensive! <Try the mail-order, etailers... buy in bulk... the "two hundred gallon buckets"...> (I have a 90 gallon).  The worst part of this is that I set up the probe and did a reading right away and it was 128! <Not atypically low...> I have read it's not good if it's under 200.  Here I had beefed up circulation, built my own sump, added good algae to a chamber, etc.  and the fish can't breathe!  Or I have too many organics!  Maybe I should have left that tidepool with BioWheel and balls, etc.  Maybe that was better!  (My nitrate was zero).  O do advise!  Thanks....... <You are learning... thank you for sharing. Bob Fenner> pH Too High? (Nope) - 08/05/05 Hello, <<Hey>> I'm terribly sorry for bothering you guys, I know you are very busy and I appreciate all your help in the past. <<No worries, happy to help.>> I have a few questions regarding pH, I was actually wondering at what level I should start to worry if it is indeed too high. <<Mmm...would strive to maintain below 8.6>> I have a 180 gallon reef with 200 lbs. of aragonite sand, about 200 lbs. of live rock.  I use a sump below the aquarium and a 42 gallon refugium next to it that is filled with various forms of macro algae, live rock and sand. <<Suggestion...keep a single species of macro algae in your 'fuge.  Algae competes for space just as corals do.  If they are fighting in your refugium they are releasing noxious chemicals to kill/retard growth of each other.  These chemicals will be/are affecting your display tank as well, not to mention keeping the algae from performing at its best as a means of nutrient export.>> On the 180 are 2x400w 20k halides and 2x110 15k VHO tubes.  On the refugium is 1x150 10k HQI and 2 65w actinics.  The sump is LifeReef design with 36" skimmer and carbon tubes.  I don't use any mechanical filtration other than the sponges in the tubes. <<Cleaned weekly I hope>> I use a Korallin calcium reactor with 10lb Co2 bottle with a fast drip and about 2 bubbles every 3 seconds (seems like a lot, but the reactor gets trapped Co2 in it, poor design I think). <<Hmm, have friends using this reactor...seem to like it fine.  I will assume you've already experimented with drip/effluent rates...measured pH of effluent.>> The system has been running for 8 months.  I've added animals slowly, I've had very few losses, algae is in check- I use a 6 stage RO and Coralife salt (and perhaps this is my problem) The source water (RO) is at pH 6.5, roughly, with an average of 5 TDS. <<Source water?  Do you mean the "effluent" from the R/O unit?.  Fairly normal readings, and a good reason to buffer all evaporation/salt makeup water.>> My ph, never falls below about 8.35 and tends to get pretty high during the extreme photo periods, I've seen 8.51 on occasion. <<Golly...these are actually quite "good" readings!  Many a marine hobbyist would love to be able constantly maintain pH values within these parameters.>> I use a controller with pH and ORP, ORP is never below 400 unless I do a big water change, at which time it dips 10-20 for a day or two, pretty normal I think. <<400 is not "normal" for most, nor necessary...would advise caution about going above this level.>> I've been toying with the photo-period on the refugium to make the pH more stable, but it still seems very high, is it dangerous at this level? <<A swing of less than .2 per day is not unstable...quite the opposite.  Your pH values are excellent in my opinion...would strive to maintain...>> My dKH is between 11 and 13, it hit 10 once when my Co2 bottle was empty and I had to wait to get it filled.  My calcium level is at 400ppm and I do not notice any animals being stressed, hard and soft corals do well, and the fish seem fine, algae is in check, present but acceptable. <<All good, but would not try to keep Alk and calcium maxed out.  The two are mutually exclusive and can cause problems at such high levels if not carefully watched (do some reading here and at the associated indexes: http://www.wetwebmedia.com/calcalkmar.htm).  I would let one or the other drop a bit.>> So, I've read, actually in a number of places, that on the reef, pH during the day can hit this level, but I was wondering if it's ok and, if it keeps rising, why and at what level I should start to worry. <<As already stated.>> Should I cut back the light on the fuge, remove a large portion of the macro algae, or leave it alone? <<Other than the "mix" of macro algae in the 'fuge and the comments on your cal/Alk, I think you're just fine.>> Honestly Baffled, Aaron <<Here's some informative reading on pH: http://www.wetwebmedia.com/calcalkmar.htm...not that baffling really <G>.  Regards, EricR>>

Re: Reactors, Probes, pH - 08/06/05 Thanks Eric! <<Welcome Aaron>> I'll prune out everything from the fuge that is not dominant. <<Tis best my friend>> I think my ORP is set to compensate for pH, it's around 350 without the compensation. <<Mmm...the presumption would be the ORP reading is more accurate with the compensation...i.e. - 400>> I believe the Korallin reactor works well, but I can't seem to get the alkalinity or calcium level lower than this, the effluent pH is 6.5- <<Fairly common reading for reactor effluent.>> I thought perhaps I could run the RO effluent through the reactor instead of using Co2, but for the few hours I didn't use the Co2 my alkalinity started to fall, and since top off water only hits the sump a few times a day it might have an adverse effect, but it could lower my Alk enough that it's not quite so scary. <<Maybe you can try reducing the bubble count of the C02...try to increase the effluent pH to about 6.8 or so.>> I'll try to adjust the reactor again first, perhaps a new needle valve will help, mines getting a bit old. <<Most of the stock needle-valves are quite "rough", I do believe the are some aftermarket valves that are more precise...at a price of course.>> I really appreciate your help and I'll add an if/then statement to the halides that turns them off if the pH hits 8.59, trip the alarms and page me. <<Ahh...a programmer eh?  All good.>> I've never seen it get higher than 8.51, and if I don't have to worry at that level, I'll start making the other adjustments you suggested. <<Yes, not a problem.  In fact, a good level to maintain.>> On the ORP though, if I turn the pH compensation off, the reading is 350, with it on, it's 400- when you say I should be concerned about this- what do you mean exactly?  Are you saying I should be concerned about the compensated ORP or the uncompensated ORP?  And why? <<Firstly, if your probe/monitor is designed to be used with pH compensation, use this measurement.  Secondly, I didn't mean to imply an ORP reading of 400 was dangerous...it's when you get much above this (over 450) that problems can arise.  Ozone is a very powerful sanitizer (more so than chlorine), It can be very useful to aquatic systems but must be used responsibly.  For most purposes/systems an ORP reading of 350-375 is adequate...I just want to instill caution when readings start to edge above 400.>> It doesn't go any higher, and falls if I change carbon, I do 2x50 gallon water changes a month and it falls a little then, but pops back in a day or two. <<All normal...and "kudos" on the water changes.>> Also- this might be a strange one, if I measure RO (effluent) with an electric probe calibrated at 7 and 10, it reads 8.95 (unbuffered RO).  I've three different probes, and calibrated one to 4 and 7- it reads RO at 6.5- <<I believe this to be "more" accurate>> but, and perhaps this is my dilemma, if I add 2 tsp of buffer (Seachem) to about 5 gallons, the dKH hits 10, and the effluent reads 7.6. <<Yikes!  Might be a problem indeed...I believe if you read the label, one teaspoon treats 40 gallons!>> Perhaps too much raw unbuffered effluent is getting near the probe and inflating my pH values- am I off-base here or should I try to send the RO through the reactor first? <<Mmm, try easing up on the buffer first.>> It's difficult to read a reagent test for anything much above 8.3- purple is pretty much purple. <<Yes, is why I prefer an electronic pH meter.>> Why do my probes, if calibrated for sea mix measure RO effluent so high?  If I use a reagent test, it shows at 6.5.  You think RO is getting too close to the probe and inflating my PH reading?  I know it's at least 8.3 with a reg test (the tank). <<The probe calibrated with the 7 & 10 reagents performs better when reading a pH above 7.0 or so...that's why I said I believe the probe calibrated with the 4 & 7 reagents was a more accurate reading (6.5) of your RO effluent.>> Is there some way I can prevent erroneous readings using RO in an auto top off system?  I add it through my overflow into the carbon chambers, but the probe is on the other side of that, I thought the drop to the sump would ensure mixing, is it too close?  Can that cause these types of problems? <<Are you adding raw RO water to your system?  Not the best application, should be buffered (properly) before going in to your system.  As for your "problems", your calc/Alk are at their upper limits, but your pH is fine my friend.>> Thanks, Aaron <<Regards, EricR>> RedOx, skimming  10/21/05 Hello Bob, I am curious as to why my ORP reading is lower (around 312) when I run my protein skimmer vs. above 400 when not using it? <Mmm, removal of charged particles, molecules, atoms by the skimmer... also increasing reaction rate... using up the 03> I stumbled upon this discovery when my skimmer pump failed and was out for a month. The ORP reading had been running 300 to 380 over the last year. Then shortly after the skimmer pump went out, ORP reading jumped to around 450. Once skimmer pump was replaced, ORP dropped back to historical levels. I am using a PINPOINT meter. I was under the assumption a protein skimmer increased the oxygen level in water column, which in turn raises the ORP reading. <Mmm, does "some things" that both raise and lower reduction/oxidation potential> I have a 90 gallon reef tank utilizing a plenum with a 5 inch sand bed. It is a lightly stocked reef with 5 fish and 60 lbs live rock. Lights on (varying intensities) for a total of 16 hours per day. Skimmer runs for 7 hours during night time. Set-up is 14 months old. Thanks for all your great insight over the years. Randy <Welcome, and I would not be (overly)concerned here. Bob Fenner> Ozonizers Bob, I read your column regularly and I note that you often recommend use of ozone generators, sometimes in conjunction with a skimmer. I was wondering if you could shed more light on the best use of ozone. In particular, I recently moved the ozone generator on my 125 fish only tank from the skimmer to a dedicated ozone reactor, so that the ozone now goes into a pressurized chamber to mix with the water and then the water and excess ozone are carbon filtered and returned to the sump. Do you think the generator is as effective as running ozone through a skimmer?  <Probably so... but you might want to do a simple couple of tests... maybe most easily detectable with a Redox meter... try testing under both set-ups... the higher Redox wins... Both should work.> What about flow rates and ozone quantities? I tend to keep the ozone set low (about 15-20 mEq/l) out of fear of too much ozone (I don't have an ORP monitor). Is there an ideal range and should I run the ozone 24/7? Is a controller necessary to safely maximize the impact of the ozone? <Oh. You can imagine my lack of enthusiasm for answering the above... It is way too easy for someone, anyone to seize upon such a measure per whatever... and have troubles... The amount of ozone you introduce to a system is highly dependent on many factors (Bioload, feeding, other water chemistry, filtration...)that can't be easily elucidated here (space/time)... I don't think you can get into trouble with a consumer unit... and I would run mine (do so) 24/7... and I would get an ORP measurer if not a controller...> If excess ozone makes it into the tank, what would it do? Are there any telling signs of ozone poisoning? <Elevate pH appreciably, "burn" your livestock... You would likely know... and this is very likely not a real possibility... As I say, most hobby units are too puny in 03 output to create any real havoc... the molecule is quite transient, and there are many countervailing influences in your system... to ozone excess> Thanks for any light you can shed on this interesting topic. >> Hopefully... sorry if this response is too (purposely) vague. I have a pitch about ozone stored in marine filtration articles at www.wetwebmedia.com if you'd like something possibly more satisfying. Bob Fenner

OZONE in Large Tank Holding Mr. Fenner, Our company specializes in live seafood holding systems, incorporating screening, BioFiltration and protein skimmers along with a well-distributed flow at a good rate through the tanks. We have concentrated on shellfish, and are being asked to do fin fish systems. Ozone is requested/ required in some cases. We plan to add the ozone at the skimmer(s) for best effect. I have 4 questions. 1. In systems of 1000 gallons or larger, should the ozone applied be based on flow rate through the treatment unit (skimmer) or based on the total system volume? <Mmm, both and with consideration to the bio-loads... it would be better/best to have a variable/adjustable ozone generation, delivery system... of a few gram per hour capacity... and a desiccator...> 2. If flow rate as I suspect, what dosage is appropriate for flow based on multiples of 25 GPM? <To be discharged where? Into the main system? Better to couple this ozone source with either Redox, pH metering in the main system... throttle up/down per load...> 3. From reading the Ozone FAQs, I conclude there is no significant risk of toxic carryover from a protein skimmer, particularly if the skimmer discharge is into a treated water reservoir or otherwise vented before getting to the holding tank. Is there reason to consider some carryover prevention process or to ensure a certain time delay before using treated water? <Not much danger here in practical "pet-fish" application. Some greater/graver concerns in your circumstances with larger generator, varying bioloads... as I say, do utilize a meter, switch...> 4. Is an ORP or other sensor recommended to control the dosing rate in this size of system? <Oh! Yes> Thank you for your assistance. Your comments and insights are extremely helpful. Roy Hobson, Tech Sea 2000 Inc. <A pleasure and honor to be of service my friend. Bob Fenner>

REDOX, O3, & U.V. Bob,  I was curious if you could point me in the direction of a source regarding the output of O3 from a U.V. sterilizer in closed systems? I know the amounts would be trace but I'm curious as to its over all effect on REDOX and dissolved oxygen.  <Wish I did have a ready source or lead here. Both Redox and D.O. are improved by U.V. ozone generation... and the amounts of O3 produced by some U.V. units are appreciable. I would contact the actual manufacturers of the units (a few links on the WetWebMedia.com Marine Links, General Links pages) and ask them in turn if they could provide you with references. Alternatively you might run on over to a large college library, ask someone to help show you how to do a computer search (in the science, technology library/section) as: http://www.wetwebmedia.com/litsrchart.htm Lastly, you might well want to do your own experiments here... using different samples of water, times, turning the U.V. on/off, measuring the values you're interested in. Bob Fenner>

Ozone question I saw awhile back you answered a question on ozone. Anyhow, I have a wet/dry system with a built in skimmer (CPR). I'm considering plumbing a small ozonizer into the skimmer (Red sea with ORP probe). Anyhow, since the probe controls how much ozone gets by, where is the best place to put the probe to control ozone amount ?  <At a point distal to the discharge of the skimmer... ideally, into a sump area where a non-hang on fractionator is deployed> Does it have to be before the actual wet/dry BioBale since you don't want too much ozone going into your bio-filters - won't it kill that bacteria ?  <Enough ozone will kill bacteria, all life> So I guess you lay a bag of carbon on the overflow to the BioBale, and put the ORP meter between the carbon and the BioBale and measure there ? <Yes, this is the best spot> Kind of lost here on trying to determine where to measure the ozone and not kill my biofilter. Thanks Jim <I understand. The ozonizer addition is still worthwhile. Bob Fenner>

Ozone Hi there Fascinating reading your FAQ pages on ozone in aquaria. One question. In setting up a system to benefit from residual ozone in the actual fish holding tanks as well as for water treatment - where would you suggest the ORP controller be placed in the water stream and how would one choose a site for a second ORP monitor in the 'fishy' tank? Andy Campbell <I would never recommend stray or residual ozone in the main display... a very precarious and difficult to monitor application. Inject ozone through a proper reactor or skimmer and pass all effluent water over activated carbon (changed regularly). If using two probes, I'd take at least one reading from the surface near the overflow. Kindly, Anthony Calfo WWM crew>

ORP Hi! <Hello> I have another technical question for you. I have a Neptune controller. When you go to the ORP setting it has an option to turn on the pH compensation or to turn it off. When it is on my tank gives a reading for 430. When it is off the tank reads 370. Which is the correct reading and what is the point of having the compensation option? <Correct reading? Mmm, they're both "correct" as in accurate for the probe/gears sensitivity/reading as a function of pH... In other words your "tester" gives different readings at different pH's... Which are indeed a reflection/mirror of the ORP at those pH's> As always you have been most helpful. Right now I have a fifteen hundred gallon system in Fairbanks Alaska and I would never have been able to do it all without your advise at every step of the way. <Glad we could "go back and forth". No worries re the Redox readings here. Bob Fenner> Bhaskar.

Become a Sponsor Features:
Daily FAQs FW Daily FAQs SW Pix of the Day FW Pix of the Day New On WWM
Helpful Links Hobbyist Forum Calendars Admin Index Cover Images
Featured Sponsors: