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FAQs on Reef Filtration: Plenum Designs

Related Articles:  Reef Filtration, Plenums, Biological FiltrationMarine Substrates

Related FAQs: Plenums 1, Plenums 2, Deep Sand Beds,  & FAQs on Plenum: Rationale/Use, Installation, Operation, Altering/Adding Media, Troubleshooting/Repair, & DSBs 2, DSBs 3, Nitrates 1, Nitrates 2, Nitrates 3, Nitrates 4, Nitrates 5, Nitrates 6, Nitrates 7, NitritesAmmonia, Establishing Cycling, BiofiltrationPhosphate, Silicates, Biological Filtration, Fluidized Beds, Bio-Ball, Wet-Dry Media 1 Denitrification/Denitrifiers, Wet-Dry Filters,

Install a secure support and screen to protect the lower substrate area/s from sand stirrers!

Jaubert system sizing?     8/3/13
Hi there guys
<Hey Dirk>
I am building a 1000Gallon size system with a 450 Gl DT
I will be installing a remote Jaubert system filtration into the system but cant find anything about proper size of this?
<Mmm, I'd buy/get and read a copy of Dynamic Aquaria by the man himself!
But, "the bigger the better"... Akin to other relative vs. (more) absolute processes to results in this universe; some does a bit of good; more is better in increments...>
I currently have an area appointed to the system which is about 25" x 20"
<I'd double this easily>

The plenum will be 1" high with 2 layers of sand on top the first being very fine (1mm) sand for about 4" then a second larger grain sand for
another 4" layer
so will this size be sufficient for any positive effects?
<Oh yes; as stated; some... But I'd have more... the whole of the bottom of either the sump/refugium/s and even the main/display tank if not having livestock that will too easily dig it up (some screening can be useful here)>
Dirk in Thailand
<Welcome; BobF in S. Ca.>

Sweeper Clown in DSB, Clown comp., plenum des. 3/19/08 I swear I've read every link and question on this page! I love your site and my husband kids me "are you reading about fish again!" My question is, I currently have a 20 gal DSB with a plenum (running with live rock since 2001) that is working great. I followed the directions precisely from Bob Goemans book on Deep Sand Beds, but it seems that reading through this site, my gravel I used is coarser than the sugar fine you recommend (I used Aragonite reef sand). I am planning to upgrade to a 120 gal (24x24x48) tank and want to set it up with a DSB also, but perhaps eliminating the plenum (as it appears to not be critical). <Correct also> My current tankmate is a Tomato Clown that loves to take her tail and sweep the bed down to the first screen. I worry that it'll upset my system, but nitrates, nitrites and ammonia are all zero, pH 8.4, sp grav ok., so she seems to not be causing too much havoc to the chemistry. My question to you is what do you think about adding a screen in the middle of my new DSB to keep her from sweeping down to the glass in the new tank? <Is done quite frequently... the "fiberglass" one (vs. metal)...> My 2nd question is around using my current bed to seed my new tank (even though the sand is coarser than preferred). Could I use the top layer to sprinkle on the top of my new sugar fine bed? <Mmm, yes> Should I throw away the bottom level or can I rinse it and reuse it as well? <Can be re-used> I'm also setting up a refugium and may use a DSB in that as well. I've read Bob Fenner's comments on keeping the DSB in the refugium versus the display tank, but I'm nervous about not having a DSB in my main tank, since it's treated me so well in such a small tank. It would be much cheaper to outfit the refugium with a DSB than the main tank, however. Thoughts? <I am the same BobF who still prefers remoting DSBs> His Reef Invertebrates book just arrived at my door last night, but not seeing as many pros and cons on that subject as I had hoped. <If memory serves, they are there> Your FAQ sections on DSB has varying opinions which is to be expected. I'm just excited about my new tank and want it to be the best home for my Tomato... she's going on 7 years old now and she deserves a bigger house. <Ahh! Have seen A. frenatus and A. melanopus clowns that have been in captive settings for more than two decades> One last question, since she is my anchor fish, are there any sites or places I can go to find the best tankmates for her? <Mmm, perhaps Joyce Wilkerson's book on the subfamily> I've read Michael Paletta's "New Marine Aquarium" and he has a nice list of fishes to put together, which would be nice if I was starting out new, but since I have her, I need to build her tankmates around her. Any input would be appreciated, have been planning for months and am looking forward to moving from planning to implementation. I love this hobby!!! Jean <Me too. Bob Fenner>

Sand Plenum Material, Use Plastic Egg Crate, Not Metal.   5/8/07 Hi guys, <A gal with you tonight mate!> First I would like to say thank you very much for your invaluable information, which has helped me alot <a lot>. <Great to hear!> I have a simple question, I wasn't able to find any egg crate material in plastic, however I did find some in aluminum. Is it wise to use aluminum in my salt water aquarium as my plenum base <Mmm, no, it is not wise to use aluminum.> or should I keep looking until I find the plastic egg crate grill? <Yes, keep looking, you might try the lighting department of your local home improvement / hardware store.> Cheers <And to you!  Mich> <Mmm please, next time use "I" not "i", thanks.>

Nutrient Export, Plenums, And More! I have some high Nitrate (80mg/l) and phosphate (3mg/l) problems in a 24month 80gallon set up. (Hope my conc. units are right). The setup gets a 5-10% water change on a weekly basis and is stable with a medium/high load of eight fish, two shrimp and a blue lobster. I tried to introduce an anemone but it never fully open and unfortunately starved. I also have a bubble algae problem. (The set up is in two tanks 55gallon which cascades its water to a 30gallon tank which then returns to a wet/dry sump in the basement with protein skimmer, mechanical filter, carbon, heater UV then back to the 55gall tank) So. my two questions. 1. Will I realistically be able to get phosphate down to a reasonable level for anemones and reduced algae? What should I aim for and will aluminium oxide be the most economic route. The phosphate comes presumably from accumulation from food. <Well, ideally, you want to shoot for <0.05mg/L on phosphate, and less than 10mg/L nitrate, if you can. I think that it is certainly possible to lower phosphate in your system. I think that there is certainly some phosphate coming from food, but there is also probably some phosphate in your source water. If you aren't using one already, you should look into an RO/DI unit, which can help you start off with more pure water. Another thought is that the mechanical filter which you are using needs to be cleaned (or have the media contained within it changed) more often (maybe twice a week). High nitrate and phosphate are definitely signs of nutrient accumulation. Attacking both together is possible. Your goal here should be to maximize nutrient export mechanisms. Your water change schedule is good; you may even want to try 2 smaller (5%) changes per week, to dilute the nutrients before they have a chance to accumulate. Also, try to really adjust your skimmer until it yields at least a couple of cups of dark, yucky skimmate a week. It may take a fair amount of tweaking, but it is possible to get good results if you work with it. I'd employ extra chemical filtration media, such as PolyFilter (my personal favorite). This stuff really works! Make sure that you are using a high-grade, phosphate-free carbon, and change it regularly. Another though would be to employ "purposeful" macroalgae, such as Chaetomorpha, Gracilaria, or Halimeda, and harvest them regularly. They will utilize many of the same nutrients that your nuisance algae are-and they will ultimately beat out the lower algae. Harvesting them essentially removes nutrients from the system directly...yep- it works!> 2. I have tee'd off a connection from the wet /dry to a 80gallon 40x20" footprint Rubbermaid container which will act as a plenum (or it could be a refugium) and new sump. The water will be pumped back to the wet/dry on a recycle loop. I am planning on using 160lb of aragonite coarse coral mix as a 4-5" bed over a 1" plenum space. <Well, a plenum is a very useful tool if constructed correctly. It does require specific void space, particle size, etc, so do read up carefully if you plan on pursuing a plenum setup. Don't deviate from the established methods for constructing plenums- the techniques and guidelines were developed after a great deal of research. Check out Bob Goemans' web site (saltcorner.com) for much more on plenums. Bob is the authority on this system in the U.S., and can really give some great input! If you opt for a remote deep sand bed without a plenum, try a fine, oolithic aragonite like Carib Sea's "Aragamax" Sugar-Fine sand, and shoot for 4 inches or more.> I have read that the plenum relies upon slight convective currents to effect as large an anoxic denitrifying layer as possible. Also since the sump/plenum is in my basement I am concerned about temperature control. I figure that I will put 30ft of 150W heating cable under the aragonite to deal with heating needs and achieve some convective mixing through the aragonite bed. Do you think this will work - will it be beneficial? <To be quite honest with you, I have not seen this done before...It is an interesting idea, but I'm not sure whether or not it is worth the effort...I'd really encourage you to contact Bob Goemans on this one!> The reason I started thinking of the cable heater is that the plenum will be in my basement which is about 40degF at the moment and only 50-55 in summer. I live in New England. I figured that the Rubbermaid tank itself (even although it will be insulated) would need some degree of heating and then subsequent small power head or air lift to get some recirculation. <Absolutely...I agree> However this would NOT help the maintenance of temperature within the aragonite bed which would depend upon conduction for its heat from the main liquid bulk. Next I figure that the microbiological rates are probably favored by maintaining a reasonably high temperature 80degF (not necessarily trying to seek thermophilic organisms). Therefore I have to find someway to keep the substrate at80degC. <Very logical approach> Cable heating is used here and there for encouraging plant growth in non-marine aquarium and this suggested to me what might work as a possible solution together with enhancing some flow through the sand bed. All the reading I have done to date - as you states - suggest some but only a slow vertical flow of water through the bed is recommended for the plenum to maximize its anoxic layer. However no where seems to suggest what is too fast or too slow. <Well, as you would probably agree-the faster and more efficiently  that nutrients are turned into energy, the better your water quality will be. So, it's important to create a system to foster these process...I do see the logic in your method...very interesting!> Even with my proposed setup I will not know what vertical linear flow rates I will be achieving anyway. My intent was to concentrate the heating cable into three longitudinal strips so that there will be cold:hot:cold:hot:cold:hot:cold strips the length of the tank (hope this is reasonable explanation). I will be using 110VAC roof de-icing cable. (I have ground fault trip electrics and will be very cautious). The cable is water proof and fully plastic coated therefore should be okay for continuous immersion. <I have no experience with this device...do proceed with caution if not using an aquarium-specific heater cable system...> Initially I intend on leaving the cable on 24hours but could put this on a timer if the mass transfer does not seem to show that the plenum is doing its stuff of removing nitrate. However I will wait 12months to be sure everything has had a chance to mature and monitor concentrations along the  way. <Sometimes standing back and letting nature do its job really is the best procedure> I must admit that I was torn between setting up a refugium in place of the plenum and instead using plants and light. Do you think maybe I should do half and half and plant Caulerpa (sorry about the spelling) with a plant spectrum 24" florescent tube on one half. <I am very anti-Caulerpa for a variety of reasons- I'd use different macroalgae for this purpose...but do utilize some macroalgae. Perhaps you may want to employ a "non-plenum" DSB in your main system, and add the refugium in line? Just a thought...> However - if I do then I will not know if the main idea ever worked.... <Ahh- the joys of experimentation!> Lastly, my skimmer is a CPR BakPak which is a small footprint venturi in-sump skimmer but only rated to 50gallon. I have not had a chance to read through all the skimmer stuff you and others have posted here - but I did see the stuff Snailman posted and this sparked enthusiasm to do this next. However I do need to finish and get this plenum up first. <Well, a skimmer is so vital to your system that you may want to push the skimmer up to number one on your list...The Bak Pak is a great skimmer- but I think it's operating at the edge of it's range in this system, so an upgrade is highly advisable here!> Lastly, lastly I did not add in the previous email that before the plenum I will be putting in a 30gallon trash can with flow distributor filled with polystyrene peanuts to act as a trickle filter to also increase my ammonium denitrification. The water will drain through the trash can trickle filter by gravity into the plenum. Currently my ammonium is 0.2-0.3 (don't know the unit) but anyway low range but detectable. I figure for minimal expense I could get more aerobic degradation. I built this piece ahead of deciding on the plenum which will presumably also achieve the same end effect of further NH3-> NO3 oxidation in addition to the anoxic denitrification. I have read elsewhere that this is not recommended as enhancing the NH3 oxidation will increase my NO3 problem. <That's my thinking...> This seems logical but at worst case if all the NH3 is shifted over to NO3 - I am only looking at a small increase in NO3 to my current concentration. Thanks for your comments and any further thoughts are appreciated. <Well, you certainly have some great ideas and a nice approach! I think that simple, biological-based systems are always best. You will be surprised at how a simple idea, such as a deep sand bed (with or without a plenum), a great skimmer, good husbandry, and live rock can do the trick. Check out Anthony Calfo's "Book of Coral Propagation" for some more information on the concepts that you touched on. Also, You may want to pick up "Live Sand Secrets" by Bob Goemans for a simple review of plenum dynamics. Most of all-Have fun! Good luck! Regards, Scott F>

Plenum, Yes! Jawfish-No! Bob, <Scott F. on call today> I have a 75 gallon reef tank with a plenum. It has been working very well. I would like to add a blue spotted jaw fish to the tank, but I'm concerned that even with the protective screen below the first layer of sand the jaw fish will disturb the plenum system to the point of severe problems with my system. What do you think? <Your concern is definitely valid. Even with the plenum screen in place, It is too disruptive to have this fish in a plenum-equipped tank, IMO. I'd rather keep these guys in a separate aquarium assembled just for their special needs. The fish will do better, display more readily, and both you and the fish will be happier in the long run. Good luck! Scott F.>

Planning A Plenum! Hello WWM crew, <Hello! Scott F. here with you> I am in the process of changing sumps on  my 130 gallon reef tank.  I have finished glazing a 40 gal tank to be used as a Jaubert Style plenum. My question to you : I purchased an undergravel filtration plate to operate as the plenum, rather than using pvc and egg crate. <To be honest, I would not use the UG filter plate. My concern is that these plates may not have enough slots and holes on the surface. This could restrict the diffusion of nutrients in and out of the plenum, and could create long-term problems. I'd really go for the egg crate. Make sure that the plenum area height is around 1 to 1-1/2 inches, BTW. > The UG plate fits lengthways perfectly, but there is a 2" gap either side width ways. <I would not be overly concerned about that gap. Just make sure that the screen is "folded" in such a way as to prevent more sand from getting under the plenum.>   I intend to use netting to cordon off the plenum, and divide the sand layers, so would this gap either side reduce the effectiveness of the plenum / render it useless ? I personally don't think that a 2 inch gap on each end would be disastrous. I'm more concerned about that UG plate, actually> Also, in terms of substrate and layers, I intend to lay a 3" deep layer of coarse sand first, cover this in netting, then add a top layer of finer sand, which will be populated by sand churning critters - does this sound correct ? <I'd use the "traditional" 2 inches of depth for the layer atop the plenum, then add the screen, and top layer of sand. It's really important not to "improvise" the plenum construction. The plenum depth, sandbed depth, etc. were developed  after many years of research by people like Jaubert, Goemans, and Gamble. These numbers do work! Lots of people who claim that plenums "don't do the job" often have not followed the "blueprints" for its construction. Don't be one of them! Frankly, I'd avoid large populations of sand-stirring creatures in the plenum system. Too many of these animals can convert some of the anoxic areas of the sandbed to aerobic ones, which can drastically reduce the efficiency of the system. If you are concerned about excess detritus in the sand bed, you can very lightly siphon the top 1/2 inch of sand, but I would not go deeper.> Thank you guys Andrew Hough <And thank you for stopping by, Andrew! Do check out Bob Goemans' web site, www.saltcorner.com, for more information on plenums from the master himself! Good luck!>

Plenum Practices! Hi <Hi there! Scott F. at your service!> Just found your Q & A site brilliant, can't find answer to my question which is about plenum filtration: Rena plates, you know the ones that snap together, if I lift them up on plastic tubes to make an inch water gap, use some plastic screening to seal the front edge (tank is a 55 gal bowfront Juwel) of the filter bed cover with coral gravel then another screen then coral sand would this produce the same effect as the egg crate plenum system.  The only difference I can see is that I would not be covering the top of the Rena plates as they only have small slots in them, the 1st plastic screen would only be placed in the front to seal the filter bed where the plates don't fit snug to glass because of the bow. <Just be sure that the window screen material "overlaps" the plates and extends as close to the front glass as possible. Also, you could expand the size of the holes on the plates. Sounds fine otherwise!> I could then use the up lift to start the bacteria process once established remove power head and up lift and monitor system before adding live stock. <Your idea sounds quite workable. Just make sure that you follow the generally accepted principles of plenum construction (i.e.; height of sand, void space, etc. These have been developed after much testing, and generally do not work well when we "improvise"!> Other filtration for this fish only tank  as well as the plenum would be: 1 Fluval 203 canister filter with spray bar the Juwel filter system (foam pads and power head) 1 extra power head for circulation (not filtration once removed from plenum system) How far off am I?? Yours, Chris <Actually, Chris- it sounds like you're on target here! For a lot more on plenums, check out Bob Goemans great site- saltcorner.com. Lots of good information from one of the leading hobby supporters of the plenum method! Have fun! Regards, Scott F>

- Plenum in 29 Gallon Mini Reef - My new 29 g tank and stand will be in this week! I purchased a 2x65 w pc retro kit (one 10,000k & one actinic). I have a BakPak skimmer (I plan on adding a hang-on refugium in the near future also). I constructed a plenum this weekend using the plans from the GARF web-site (eggcrate sitting on 1 inch PVC covered with nylon screen). I have a couple questions about the plenum. I planned on using 100% live sand (3-4 inches) instead of the suggested substrate on the GARF site. Will this be a problem?  <Probably.>  Will the sand stay on top of the nylon screen or will it eventually work its way down into the plenum?  <It will work its way down in time.>  Could I, or should I use a thin layer of crushed coral directly on top of the plenum underneath the sand bed?  <Yes.>  The DIY plans call for a second layer of screen to be placed in the middle of the sand bed to avoid disturbance to the system.  <Correct.>  Is this second layer of screen necessary in your opinion?  <Yes.>  Also I plan on adding approximately 30 lbs of live rock. Should I add the rock and sand at the same time?  <Yes.>  Thanks for your help. I'm trying to get all the help I can to avoid too many alterations in the future.  <Honestly, I'd skip the plenum in your case - you just don't have enough volume in the tank to sacrifice this space, and because of the small size of this tank is going to give a net effect of almost zero. I think you'll have more problems than solutions with this setup. Would be better off just doing a deep sand bed with live sand and use the live rock.>  Thanks for maintaining the great site. <Cheers, J -- > 

Type and depth of sand for a plenum Hi, first time writing in so a little nervous, please be gentle.  Have read many articles on WWM, in fact so many that I think my head is going to explode.  My question is about my plenum, I had a plenum system 55g, setup for 4-5 years, everything was great, but then things started to die off, the coralline and fish etc. so I tore down the system cleaned out the plenum and put it back in, with 2" of crushed coral on top of the plenum and NO sand. << I'm not sure the plenum was the problem from the first time.  I don't think I would have removed it and started over. >>  Now I know from reading at WWM that this is the wrong way to do it.  So my question is this, can I just add the sand right on top of the second screen, on top of the crushed coral? << Sure can. >> Or do I need to tear it down and clean the crushed coral (replace?)  Will the crushed coral be full of gunk that I need to clean out first? << Was the crushed coral used in the tank previously?  If so, I'd probably take and wash it out.  If not, then don't worry about it. You can add sand right on top.  I'd do this slowly adding a half inch at a time.  It will slowly work its way down and go beneath the crushed coral. >>  Or will putting the sand on top be ok?   It has been up and running the  way it is now,  for close to a year, no sand on top of the plenum, so I wasn't sure if just putting the sand on top would be ok, or if it would just trap a bunch of gunk that is in the crushed coral.  << If it has now been up for a year don't do anything.  Just let it keep going. >> Also one other thing, you talk of  a DSB needing to be 4+, why does a plenum setup not need to be that deep, I am assuming because of the plenum? << I would still have it that deep.  I think 3" is perfect with or without a plenum. >> Does the sand on top of the plenum need to be deeper than 2"?  << I don't know if it needs to be, but I think it will do better if it is 3"-4". >> Ok I think that about covers it.  Thanks for your help and I love the site. Thanks, Robert Cline <<  Blundell  >>

Plenum Vs. UG Filtration 4/1/05 Howdy Bob and Anthony. <Howdy> Anthony, I've received and read your book. Marine life is simply amazing isn't it? I have ordered your and Bob's book of reef inverts. Can't wait. <Thanks kindly!> Well, as you have both told me, I am actually running an undergravel filter instead of a DSB/Plenum (I assume due to the risers and powerheads). 55 and 33 gallon tanks. Question is, I am re-vamping my 90 gallon for my farming project and would like to know the benefits of true DSB/Plenum vs. UG DSB/plenum systems. <Ahhh... When the "Reef Invertebrates" book arrives, you will have our current opinion at great length... about 100 pages on live sand, DSBs, refugia, plants and algae!> (90 gallon used to have 4"crushed coral bed and Nitrate levels off the charts :() My UG tanks are actually doing quite well, except the pH will not stabilize higher than 8.1, buffered every day.  Simply put, would you recommend DSB on bare glass, DSB on plenum with no risers, or DSB on Plenum with risers? <A static bed on bare glass is fine> I am open to any of these, I do love the looks of the DSB. I want a pH of 8.3, as I would like to do mass Xenia production in this tank. Does the rapid denitrification process of the UG/DSB really hurt my dreams of 8.3 pH, or should this be possible in time? <On the contrary... DSBs support Ca/ALK, and pH> GARF suggested the UG/DSB/Plenum, but advised removing risers at later dates. <It's a waste of time IMO> I have read article after article regarding this matter and everyone has different ideas. <Mine are backed up with the use of 48,000lbs of oolitic sand, 5,000-8,000 galls of saltwater, and over a decade of experience FWIW> I believe you and Bob come across as having the most knowledge of all who I read from on this subject. (No offense to WWM crew of course) BTW, I chopped the heads off my mushroom Sarco only to find the insides rotten. <Ughhhh! Sorry to hear it> All frags doing great, but the mother colony has these little brown "bugs" crawling around on the freshly cut stumps. I left 1 head and cut 2 heads off. All frags and momma head doing great visually. Should I be concerned with these bugs? <Its hard to say with a pic or better description than "bugs" <G>. They are likely no trouble> Broad question, I know, but these little guys are like the size of a "speck" or grain of sand. They do move around if I poke them. This is my broodstock tank and I want to be careful here. Thanks for everything guys. Your pupil, Mike Toole Detroit, MI <With kind regards, Anthony>

Dinosaur marine undergravel filter - Hey, if it works! 11/1/05 Bob. after reading several opinions from your website, it seems my undergravel filter system is out of vogue according to several experts. <Heee! Define "vogue", "experts"...> I have had this setup (twin filter plates in 55 gal tank, 2 powerhead 400's in back corners, a Skilter 400 skimmer/filter system and full length Coralife lighting). I don't want to remove my filter plates if possible. Would blocking my uplift tubes or a reverse flow system be better alternatives? <Yes... would create what "modern experts" call a plenum> What precautions should I take be bore converting to either method? <None really... could perhaps add a bit more substrate. Please read here: http://wetwebmedia.com/Plenums.htm and the linked Related FAQs at top. Cheers, Bob Fenner> Sincerely, Randy Stewart  

Amount of substrate Bob- If I resituate the NNR in the sump then how much substrate should I put in the main tank, how big of a sump do you recommend and what type of lighting should I use in the sump. Also, should I place some live rock in the sump as well. Do you recommended this because it is more effective or because the amount of substrate in the main tank is ugly to look at? Thanks again. Rob The biggest sump you can fit is the best... And about the same amount of depth... depending on the grades of substrates used for the NNR in the sump... and Yes, I'd place more live rock... and a light over the sump/NNR... and culture Caulerpa there... with the light on 24h/day. and a blend or preferences re resituating the NNR to the sump... both, but more functionally versus aesthetics... It's far easier to manipulate a remoted NNR than thrashing about in your main tank! Bob Fenner Hi Again Bob, I'm not sure I understood your response. Did you mean it's OK to use 2-3 inches of sand without the plenum? If not, what problems would/could I run into down the road without a plenum? Thanks, Tony >> Yes to the three incher... And all sorts of anaerobic nasties problems are possible with poorly built, maintained plenums... algae outbreaks, hydrogen sulfide wipe-outs, a loss of any appreciable calcium...  Bob Fenner

Plenum in the Sump A couple questions I thought of as I planned my building of a plenum in my Rubbermaid 40G sump. There is very little light if any (even during the day) in my sump because it will be in my stand that is located within an alcove in my home. Is there any reason (or benefit) of having a light on over my plenum/sump? The Caulerpa will be in the filtration compartment turned refugium in the back of my Sea Clear System II tank. <Hmm, yes... if you intend to put some sort of photosynthetic life in the sump/refugium... I would... and it will make it easier to work on...> Do I still need to "churn" the sand in my remotely located plenum? I guess I would do this by hand because it's in the sump? How often? <Not much or often... maybe half of it a month, just the surface... i.e. not the larger grade material beneath the mid-screen...> Are there any benefits of 4" of total substrate as opposed to the 3" (1.5" each) you suggested? <Mmm, yes... if sufficient/proper grade, shape/angularity... more is better... if not and the material channels, clogs, no...> As you know, the Rubbermaid container is not "see through", so I will only have the top view of the plenum as visible. Is there any warning sign of a problem I might miss by not having the side view of the layers? Build up of "black areas" as an example? <IMO/E, not really... smell can be a clue... but measuring, recording the alkalinity, some biomineral like calcium will tell you enough "of the story".> What type of sand should I use on the top layer? Live sand or regular aragonite and wait for it to become live.  <The latter in all frankness...> Because the plenum is in my sump and has no live rock above it, there will be not much to make non-live sand turn "live"... is this correct?  <Not really... anything live in any part of the system will quickly find its way (if it lives in such settings) to the "sand".> I don't mind spending the extra $$$ if there is a benefit to using the already live stuff. <Not much in this set of circumstances... I would place live rock, some Red and or Green algae/s and lighting here as well though.> Thanks to you as always, Eugene <You're welcome my friend. Bob Fenner>

Plenum in my sump? I almost hesitate to ask you another question, for the fear of being burdensome, but I really appreciate your quick replies and candor. <Okay> To recap, I have a 55 gallon fish only tank with live rock and live sand. The purpose of my next project is natural nitrate reduction and increased water capacity. Should I build a sump or a refugium? <A very good route to go> I only have room for about a 10 or 15 gallon tank inside my stand. My wife will let me do whatever, as long as I don't take up more space than I'm already using! :-) <I understand> Will a plenum sump or a Caulerpa refugium be "better" for lowering nitrates? <Overall... the Caulerpa if you had to choose... you don't have to... you can/could have both in the same sump...> Does the water "sit" in the plenum sump long enough to get pulled into the plenum for nitrate reduction? Especially in a small 10 gallon sump? <Hmm, yes... enough... Brownian motion, osmosis occurs... with agitation/circulation by whatever pumping mechanism you're using to move the water thither and fro> You mentioned the use of Lights of America florescent lighting. <I did?> So their standard bulbs' Kelvin rating is sufficient for Caulerpa?  <Close enough...> Can you have too much light?  <It is possible...> I have their 55W florescent flood lights (http://www.lightsofamerica.com/outdoor.htm model 9027) which gives off a lot of white light, but I'm not sure if it's the right temperature for Caulerpa. I have two, and outside of the California energy crisis, I have no problem with using both if it will benefit the plants. My friend who used to work there thinks that they're around 4,000K - 5,000K. <Some, yes... best to test for yourself...> Whether I create a sump or refugium, here's what I plan to do... please give me a thumbs up if you think it will work... I'm concerned with functionality, cost and of course NO FLOODS. <Okay> - Purchase a CPR overflow to take water out of my main tank. - Hook up that overflow with rubber tubing to siphon? <Yes> water down to my sump/refugium. - Fill the sump/refugium with: - If Sump: all that stuff that makes up a plenum system - If Refugium: small pieces of live rock, no substrate, and a lot of Caulerpa - I assume only about 70% full of water to account for "backflow" <Hmm... do "practice" this by purposely unplugging the recirculation pump... marking the sump at the "highest" full point...> - Lights of America CF lights - A RIO 800 pump (or do I need larger) <S/b big (pressure/flow) enough...> placed inside the sump/refugium with the output connected to rubber hose to push water back up to the main system. Can I put the end of the rubber hose inside the last chamber in my main tank's protein skimmer so that there is only one return tube inside the main tank?  <Yes... just make sure it is secured from wiggling free...> I assume because it's a overflow type return tube on the CPR BakPak, it won't overflow the protein skimmer. <Likely not> Is it really this simple? Or am I missing something that will cause my system to flood or be harmful to the aquarium in any way? <This IS about it... Bob Fenner> Thanks as always...

Re: Plenum in my sump? Will a plenum sump or a Caulerpa refugium be "better" for lowering nitrates? <Overall... the Caulerpa if you had to choose... you don't have to... you can/could have both in the same sump...> So you recommend a 15 Gallon Plenum Sump with Caulerpa growing in it? I wasn't planning on partitioning the sump so it would be one main area. Can this still work or should I just go the Caulerpa route? Much obliged.. <I would do the "both" route here... even w/o partitioning the sump in any way. No worries... and you will find nitrates greatly reduced by utilizing both a means of denitrification AND uptake. Bob Fenner>

Moving Substrate to sump, and what kind of Carib-Sea to get? Bob, Thanks for your help recently. <You're welcome> I'm adding a 20 gallon or so sump to my 38 gallon FOWLR. It will have a plenum and macro-algae. I currently have Carib-sea Geomarine crushed coral in my main tank, about 1" deep. I want to change to sand in the main tank. <Good idea> Three things: I want to use the crushed coral from the main tank as the bottom layer in the new plenum for the sump. Is this the right size crushed coral for the bottom layer, and is it o.k. to use the current crushed coral? Or is there a better bottom layer material. <Should be okay... use a plastic screen mesh (like material available for screen door replacement) on top of this layer and finer material (likely coral sand) on top...> I want to change to sand in the display tank. I'm hoping you are familiar with the different Carib-sea kinds of sand. <Yes> What is the best choice for the main tank. It won't be a deep sand bed. The choices are Carib-sea pure Caribbean Aragonite(0.18-1.2mm), Carib-sea Aragamax(0.5-1.02mm), or Carib-sea Special Grade(1-1.7mm) I would like to have a blenny or starfish in the main tank. <Myself... would go with the last (Special Grade)> Of the three Carib-Sea choices above, what is the best choice for the top layer of the plenum? <As stated> Thanks a million, you're an excellent resource, and your book should be arriving on my doorstep today courtesy of UPS. Dan <Be chatting, and taking up your time... pleasurably, my friend. Bob Fenner>

Plenum/Refugium Substrate Bob, Hello! You have a wonderful and informative site which is surely just and extension of your personal endeavors. I have read quite a bit of your information posted and do my best to check out each day's question and answers for odds and ends that aren't necessarily covered in your categorized postings. <Glad we have found each other> I have the following question for you: (in summary) What would you recommend that I use for the substrate in the following setup: 180 gal w/overflow to 50 gal sump Sump contains: Aqua-C EV150, heater, return pump(2500 g/hr pump @ 6.5' of return 3/4" tube), 20 lbs of live rock, and constructing a 16"x28" plenum/refugium(24hr lighted with Caulerpa) <Crushed coral of a "medium" grade... #5, or nominally about an eighth of an inch diameter (for looks, function in this size system)... unless (here come the necessary stipulations, alternatives) you wanted to build a plenum here... or have organisms in mind that require smaller, larger, mixed aggregate...> Mentioned above is a "work in progress" sump upgrade as I currently have a temporary 29 gal (old unused fish tank) supporting the return pump, live rock, and culturing Caulerpa. The temporary skimmer is a CPR Bak pak. I'm currently breaking in the Aqua-C with recycled water from today's water change, and one of the overflow sponges which was heavily soiled.. (I mixed up some really nasty water to break in the skimmer while I finish building the sump). OK, where my question comes... should I use aragonite sand in the plenum/refugium? (wouldn't it dissolve and get clumpy. provides calcium/buffering capacity, but I would have to tamper with it a bit on an annual basis to replenish)... <For this size sump, main tank I'd probably just use live rock in the sump... not make it a plenum... not really large enough for all...> if regular maintenance is required anyway, should I purchase "Miracle Mud" (...do you advocate the use of this? <A possibility... would start off w/o it at this juncture. Though am a fan and friend of Leng Sy, the owner, manager of Eco System> Michael Paletta seems to be a little more than just a "user," more like he is sponsored by "EcoSystem Aquarium."  <Do know Mike... and he isn't paid at all by Leng... he is just enthusiastic about the application...> Very little information is available around the web with research/experiences), <Do consult with the various electronic bulletin boards, chat rooms here... there are many vocal folks with experience out there. Ours: http://talk.wetwebfotos.com/ ... look for Des> or should I use non-aragonite sand.  <Crushed coral would be best all the way around, for most applications... calcium carbonate based at the very least should be your goal> My plan is 4-5" of sand,.. hmmm, would all 3 be beneficial in specific substrate layers? The sand will be suspended by perforated ¾' tubing (as the supports, laying on their sides), plastic egg crate layer (across the tubes, suspended above the plenum floor), and covered by a nylon screen to prevent the sand (and micro-inverts) from passing through. <Oh! Please see: http://wetwebmedia.com/Plenums.htm> BIO load - 2 sm Sailfin tangs, flame angel, 3 damsel fish, 3 small patches of polyps, 100 lbs of 3 yr old live rock. Of course, this is an ever running work in progress, this was a 3 year established 55 gal tank. And since my recent honeymoon(1 month ago) to Maui, HI, there will be plenty more upgrades. We (my wife and I), became SCUBA certified while honeymooning and spent 8 of the 14 days diving and/or snorkeling (diving gets expensive!) <There are ways to reduce costs... as you will learn> in the Hawaiian waters! (Molokini is best!) <A fabulous compressed cinder cone for sure> My wishes to anyone who loves the marine life, please, find the time and the money to go visit the life that you love in their natural habitats. There is so much to learn. <Wish I had written the above! Wait, think I have once or thrice> (And fun to just watch and admire!) (Not only helps your own appreciation, but it also helps when your spouse is able to see for their self what its all about'¦ it's so much easier when the person who is sharing the bills also appreciates the hobby! '¦but be warned, it's only a slight advantage. :) <Amen> Thank you for taking the time to look over all this, and your considerations. -herb <Be chatting my friend. Bob Fenner>

Plenum question I just finished reading your article on Wet Web Media.com, and was wondering if your used the same substrate through out the bed will it effect the way it works? <Which article, which "way"?> I wondering because my local fish store sells the CaribSea reef sand and they sell live sand which is from their stock of CaribSea live sand tank, it the same grade of reef sand. So is there a reason for using two different types of grade such as crushed & sand? <For some folks... by and large in small captive systems one grade is best/better> Thanks for any help in this matter. I'm am setting up a 120 gallon tank, I'm stuck on the right way to go about setting the plenum up. thanks again, Tommy <Ah, for a plenum... here it is better to use two grades... Please see: http://www.wetwebmedia.com/Plenums.htm and the FAQs beyond. Bob Fenner>

Plenum Design I wrote you recently about my 220 gallon sand bed reef tank. Your advice was to start over, which I am doing tomorrow, If I want to do a deep bed, would you recommend all fine sand or medium deep with fine on top? <Two grades, levels... as posited on WetWebMedia.com> I was not planning on a plenum this time. Do you recommend a screen between layers? Thanks! Ron

Re: Plenum Design I am sorry, I looked through FAQ and can't find my exact question's answer. I take it you recommend 2 grades of sand. Screen? Thanks. Ron <Yes my friend. Sorry for the trouble. Please see here: http://www.wetwebmedia.com/Plenums.htm and the FAQs beyond. Bob Fenner>

Plenum Bob & Co., <Steven Pro here this evening.> I am thinking about using a simple filter pad (1/2 in thick) along the bottom of my tank as a plenum of sorts. Of course will add aragonite etc. My thoughts are that the pad with its thick maze of plastic media will allow for the anaerobic denitrification sought in a typical plenum while giving surface area for the bacteria to proliferate. Am I off here? <I think that a 1/2" filter pad underneath 4" of sand is quickly going to become a 1/10" filter pad that is no longer porous. If you wish to do a plenum right, I would search for some instructions from Dr. Jaubert. Many plenum systems have had problems and many of those problems can be traced back to an incorrect setup.> Sincerely, Dennis Mao <You are welcome. -Steven Pro>

Plenum Riser Function?? Howdy to all! <Jeff> First, thanks for your VAST resource of information. Well I have started 2 new reef tanks for coral farming and propagation. Anthony, I have your book ordered.  The tanks are 33 long and 55. Both started with plenums and DSB. Let's use 55 gallon here....(As both tanks have same results and questions)  4-5 inch sand bed. 3/4 reef grade coarse sand, 1/4 sugar fine and live sand, all aragonite (All CaribSea) with a mesh screen 1/2 way down. As per the instructions I followed (at GARF), I installed a riser tube and have a 665 GPH powerhead on it. All seemed very well. ammonia, nitrite, nitrate all zero. Alk 4.0-4.5, Calcium at 400-450.  Two Questions:  1) I was told to remove powerhead from riser tube when ammonia and nitrite levels =zero. The tank cycled for 1.5 months (from startup) and all was great. Upon removing powerheads, I found my tanks almost crashed. Ammonia=.50, Nitrite=>1.0, Nitrates at 15-20. I promptly re-installed the powerheads ( after 40% water changes had little to no affect on Ammonia and Nitrite) and overnight, the readings were back to perfect. I thought I wanted a dead water space under the plenum. Yes, No? <Mmmm, well... yes... but what you had, have is not a plenum... is actually a latter day undergravel filter... replete with aerobic microbes... nitrifying bacteria...> 2) I seem to have a pH problem. 8.05-8.10 is where it stays, even adding buffer. I assume the answer has to do with the lack of fresh air, combined with CO2 from keeping all tanks in basement. I thought pH would be no problem, with having over 100 lbs of aragonite substrate.  <Mmm, maybe some... but more from your "speeding up" nitrification in the sand bed... this is a reductive process (as in ReDox... reduction/oxidation... aka acid-base chemical reactions... the stealing or giving away of electrons...> Again, thanks in advance as you guys are freakin' fantastic! <Whoa! Take it easy! We're just a bit more experienced pet-fish types like you> BTW, No skimmers running yet, only 2 Sarco's in 55 and 2 colts in 33. I am picking up a phosphate test kit tonight to see if that is my problem.  Mike Toole - Detroit, MI <Mike, do turn your skimmer on... Bob Fenner>

Cold Feet? (Plenum Setup) 4.3.05 Dear all, <Just Ryan with you today! Sprung forward an hour, and feelin' it!> Please help me with some advice on setting up my new tank. I am upgrading from a 70g tank to a 130g FOWLR, he main difference being that I will now have a 70g sump. I am having fun working on it and plumbing it all in without the usual inconvenience of having water in the tank. I had decided to go with a plenum system on the advice of my local retailer, but after spending weeks reading through massive amounts of debate on the net, your site, books etc, I'm just getting more and more confused and worried about it. A main source of problem for me is getting the latest thoughts, as I don't see many new works on the subject. Loads from the 90's, such as my Tullock Natural Reef book, but not so much recently.  <Today's SPS craze has pushed demands on water quality through the roof- And thus the technology is born and evolves. Today's use of high quality live rock, precision skimmers and or refugia, and current/wavemakers seem to have great results...But a plenum represents a simple, effective, filtration method in the right application.> Going through all the FAQs is also confusing with different people giving different ideas, and no dates given, though it seemed clear that DSBs were gaining favour.  <We have recently started dating the queries. However, I don't think that the effectiveness is lost: They have forced you to visualize the entire process, in more ways than you thought possible!> If I do a plenum system in the sump, with a lower layer of coarser 1-2mm non (less) soluble sand, and an upper level of fine sugar sand, both 2-3 inches deep, with screens between, is this still currently thought of as OK?  <Yes> I will be using my skimmer. Is it best to put much live rock / macro algae on the bed and use lighting? Or is it better to go without the plenum and just use a DSB? <I'd skip either in favor of a nice circulation system and well maintained refugia. Although you haven't mentioned what type of bioload/ecosystem you're interesting in keeping, refugia opens all types of doors, without sacrificing nutrient control ability.> Thanks in advance Peter Southampton, England
<Good luck! Ryan>

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