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FAQs about Marine Substrate Anomalies: Troubleshooting/Fixing

Related Articles: Marine System Substrates (Gravels, Sands) by Bob Fenner, Marine Substrate Options by Sara Mavinkurve, Deep Sand Beds, Live Sand, Biofiltration, Denitrification, Live Sand, Live Rock, Biominerals in Seawater, Understanding Calcium & Alkalinity,

Related FAQs: Marine Substrates 1, Marine Substrates 2. Marine Substrates 3, Marine Substrates 4, Marine Substrates 5, Marine Substrates 7, Marine Substrates 8, Marine Substrates 8, Rationale, Selection, Reef Substrates, By Type: Aragonite/s, Coral Sands, Silicates, Dolomites/TapAShell, Southdown & Such, Collecting Your Own, & Physical Make-up, Size/Grade, Location, Depth, Cleaning, Replacing/Adding To, Deep Sand Beds, Refugium Substrates/DSBs, Live Sand, Mud Filtration 1, Biofiltration, Nitrates, Aquascaping, Sand Sifters for Marine Systems, Calcium, FAQs 1,

Pockets of sand turning black beneath SHALLOW sand bed      4/29/13
Hello crew,
First, just wanted to say thank you for all the great info on this site! I rely on WWM and Bob Fenner's books for reliable info, so I hoped you could help me with my question.
<I hope so too>
I have a shallow sand bed in my reef tank (perhaps 2"). I noticed recently that the sand in one of the back corners of my tank has turned black in pockets beneath the surface (see pic, which is quite zoomed-in).
<I see this>
I've heard of this happening when hydrogen sulfide builds up in DSBs, but I have no idea how it happened in such a shallow sand bed.
<Can do so>
 I normally vacuum my sand bed when I do water changes, but this area in the back corner seems to have been neglected.
<Ah yes>
I've been told that under no circumstances should I disturb this spot by vacuuming the substrate, or I will release the toxic buildup and kill everything in my tank.
<Not likely; no. I would vacuum here>
I hope this is not true. Would you advise vacuuming/cleaning the sand in this spot?
<Yes I do>
Thank you so much for any insight you can offer-- I'm terrified that this is going to end in a tank crash! :(
<Not to worry. With the vacuuming, most all the material in question, of danger, will be removed. Bob Fenner>

Unknown sand issue      8/14/12
Dear Sir,
It has been suggested that I contact you about an ongoing sand issue in my 90 reef tank. I have searched and read through tons of posts on your site, yet I have been unable to find a solution to my problem or even to figure out what it is. I will attach 2 photos (sorry, I'm a POOR photographer) so that you can see what it is. I will also do my best to describe what I see.
<Unfortunately, no pics attached. Please try again, including sending them back to yourself>
Tank and water specs:
90 gallon with center drilled overflow
20 gallon sump/fuge
120 gph Eshopps skimmer
RODI water with IO or Seachem salt (RODI 47 ppm in, 4 ppm RO, 000 ppm DI)
2 inch sand bed consisting of pink and white sugar sized Fiji sand
105 lbs of Vanuatu, Fiji, Pacific shelf and random base rock in the DT and sump/fuge
10 fish, over 30 snails of various types, 11 or so coral colonies and frags
1x Koralia 1400 gph and 2 x Koralia 750 gph power heads plus 612 gph (corrected)
return pump in the display tank
GFO is run 24/7 in a Two Little Fishes 150 Phosban reactor
Carbon is run every other week in a matching reactor Filter bag is run one week on, one week off Lighting is a combined total of 110 LED's, dimmable with a max power output of 240 watts. Currently running at about 35% power. Actinics are on for 12 hours, whites for 8, indirect actinic is run for 6 hours as moonlight.
This tank is almost exactly one year old. When cycled is went through a very soft cycle. At 2 + months its did have a Cyano outbreak. Combined methods of blackout and chemicals
 were used to correct the issue. It has had one ick outbreak and one fish was lost. Several Zoanthid colonies have been lost.
changes are done weekly. Water parameters as of 12 noon 8-13-12 are as follows:
pH 8.0
Ammonia 0.0
Nitrate 0.0
Nitrite 0.0
<Photosynthates need measurable NO3... and HPO4>
KH 5.5
Ca 440
SG 1.026
Temp 80.1* F
This issue I have is a black gunk on my sand. Its breaks up but not completely.
Flow does NOT seem to affect it. When removed for visual inspection is does have a green tint to it. There is no smell. It does not feel slimy to me. It does not appear to me to have a root structure. Interestingly enough, it seems to go away in the dark. When the lights first come on in the morning, it is mostly gone. It gets worse as the day progresses. If a sample is removed and allowed to air dry however, it remains visible.
Do you have any idea what this stuff is and how I might rid my tank of it?
It is very unsightly.
<A look-see through a microscope would likely solve this mystery. Some type/s of algae I suspect>
For photos, see:
<Mmm, from the pix, your description of the system, loss of Zoas... likely mostly a Cyanobacteria population>
Thank you for your time,
<I encourage you to consider the array of competitors, sand stirrers, use of DSB... many approaches to control... Gone over here:
and the linked files above. Bob Fenner>

Re: Unknown sand issue     8/14/12
Thank you for the reply. Let me clarify some of my original message and answer some of the comments you had.
First, I run GFO due to positive PO4 test.
<I would "goose" your Kalk alkalinity here instead... kick the pH to about 8.6 or so, to insolubilize the HPO4, kill off this mess in one go>
I know that these are notoriously unreliable but choose to eliminate the possible bad effects of PO4 in my system.
When tested, with the API titration kit, I show between .25 and .5 ppm.
<Again... IF you have photosynthates, this reading is no big deal... is necessary>
To clean up the Cyano outbreak I had, I did a 4 day blackout. This had only minor positive results so I dosed Chemiclean and the problem was gone almost overnight. Carbon was run and systematic water changes of 10% were done over the next 12 days until 120 gallons of water had been changed. The water change schedule then went back to once a week, 10%.
As for my test results...... I do not currently test for Mg.
<I would... s/b about three times [Ca]>
 I also do not trust that the API results are 100% accurate for the nitrate readings. My reasoning for this is that my tank is right on the limit for stocking and it has been suggested that I am also verging on over feeding. I have 10 fish in my system. 3 Chromis, 1 Damsel, 1 snowflake clown, 1 Maroon clown, 1 Foxface, 1 dwarf angel, 1 Royal Gramma and 1 Scooter Dragonette. I feed a maximum amount to minimize any aggressive behavior. To this point I have been successful. All my tank inhabitants are peaceful towards one another. Yes, I realize the clowns should not be in the same tank, but that's another story. When I do see issues, one will be re homed.
I will take a look at your link and see if I can figure things out for myself, but may well be back to ask more questions. If it does turn out to be a form a Cyano, what would you suggest to eliminate it?
<... please read through what is posted on WWM re>
I am hesitant to o through with a chemical treatment with Chemiclean again since many forms of bacteria build up a resistance to medications.
<Not suggested>
 I don't want a tank crash! My feeling on DSB are not positive. I have read too many bad stories about people who slipped and disturbed the bed causing the deaths of everything in the tank.
Thank you again,
<Welcome. BobF>

Sand bed problems    3/25/12
Dear Crew,
  First and foremost, thanks for all you guys/gals do! I have a 125g reef has been set up for 2.5 years now. I guess I should call it a former reef, as I just had a cucumber die I didn't know about, which resulted in a 4ppm ammonia spike that pretty much wiped everything out for my corals.
<No fun>
My Mini-maxi anemones survived as well as all my fish, but the rest of the corals are either gone, or finishing out melting away. I started doing 25% water changes every 3 days, while using AmQuel to try and get things back under wraps, but I have a feeling my coral collection will soon be down to nil. Anyway, on to another dilemma. I recently have noticed over the past few days that my sand bed has be accruing dark grayish to black spots I am not used to seeing. I am hoping it's not hydrogen sulfide, but I have a feeling it is.
<This mix isn't good>
I just wanted to try and confirm it with you as I try and let things settle down in the tank. I am hoping it will clear up on its own, but I am not really sure what is going on. If you could let me know, that would be great. Thanks Crew!!
<I would definitely be vacuuming this stuff away... systematically, like one half or one third of the tank bottom per maintenance/water change period. Bob Fenner>
p.s. Sorry for the larger image size, but I thought I would try and do the best I could with getting a nice clear image to see.

PH, stkg.... 10/4/11
Hey guys and gals!! Hope you can answer a couple of questions for me. I am sorry they are all over the place but I wanted to send 1 email. First, I have a 150 reef with about 200 lbs of live rock and 75 lbs of live sand. I live in West Palm Beach Florida and have an endless supply of water and sand in my back yard. I have read on here a hundred times the sand from the beach is not so good but decided to give it a shot any way.
<Can work>
The tank is stocked with a Blue Jaw trigger (male), a pink tail trigger, a pearly jaw fish (looking for a second), a pair of ocellaris clownfish, a mandarin goby, a cleaner wrasse,
<The last two... you should read about on WWM>
a forktail blenny, a lawnmower blenny, some peppermint shrimp, cleaner shrimp, and a mated pair of coral banded shrimp, about 30 snails,
<These last four... surprising the Balistids haven't consumed them>
a Sandsifting starfish, a 4 inch Halimeda plant, and a pink and green cucumber. The ALK of the tank is around 13 dKH. The tank parameters are: ammonia is 0, nitrite is 0, nitrate is .5,
<How is this kept so low?>
phosphate is 1ppm, and calcium is at 400. My questions begin with my PH. The PH never stays at 8.3 but rather stays around 7.8 to 8.0 I buffer the water just about every day with Seachem marine buffer and the PH goes to the 8.3 like it is supposed to only to drop over the next 24 hours back to the 7.8 -- 8.0 range.
Is this due to the sand?
<Might be>
If the sand is the issue is there a way to fix the issue without getting a new substrate?
<Keep vacuuming it for one... add more base rock>
Will mixing some aragonite in with my current substrate help?
<Should; yes>
My next question is about the coral banded shrimp. They have made a cave their home and defend it against any fish that comes close. They do not attack the fish but simply push them out of the cave. Is this normal or is it going to become an issue?
<Not likely in this size/volume>
Is there a sea slug or Nudibranch that is good or will be helpful or should I stay away from them all?
<The last. Bob Fenner>

Hydrogen Sulfide Issues, 6/8/11
Aloha Everyone!
I am very new to the reef keeping hobby (with the sleepless nights this venture has caused I'm going to start wondering why I'm not getting paid to do this)! I spend countless hours on your site, and it is definitely a WEALTH of good information and advice for people like me, thank you for having it! My husband is always telling me to get off the computer these days, must be a sign! I am going to apologize ahead of time for being long winded. but I think that all the bits of info may help you help me!
<No problem.>
While I have done a lot of searching for answers to my questions, I cannot seem to find the answer that suits my particular problem. I am currently cycling a 125 gallon tank, which I hope one day will be a fruitful reef tank. I bought this setup on Craigslist, as it was basically in new condition and a steal, considering. I am running an Eshopps wet/dry filter with an Iwaki return pump (some research does alert me that the turnover rate is too low for this tank and I am currently searching for a new Iwaki that won't bankrupt me). I'm only getting about 6 turnovers per hour.
<Far too low, looking for like 20X turnover, this can be accomplished by the use of powerheads or a closed loop system, it does not all have to run through the wet/dry.>
That return pump is connected to a SCWD (pronounced squid) contraption that creates this wave maker like flow in the tank. There is enough pressure to push around the sand and debris at the bottom of the tank, and the dreaded glass anemones that hitchhiked on my live rock are swaying pretty hard in the turbulence. I have wonderful surface agitation as well. I am also running a Euro Reef skimmer that does one heck of a great job in this tank.
There is also a plenum on the bottom of the tank. As far as the substrate goes, everyone (including my LFS) looked at me funny when I asked for "live sand" for the bed of my tank. They gave me a kind of. don't you know you live in Hawaii. you're surrounded by sand kind of look. So against most of what I read about harvesting sand from the ocean, I went to the most remote beach I could find and scooped up two 5 gallon buckets of sand. Needless to say, I now have all kinds of critters that are still amazing me about 4 weeks into this cycle. In my opinion, the sand ranges from fine to medium grain. I have about 10lbs of live rock that I picked up from my LFS, and about 40 or so pounds of rock that we took from the beach. This is not the pitted rock you see in most reef tanks, it's just some rock that had really nice patterns of coralline algae on it that I thought would look nice while we cycled the tank.
<Sounds nice, but I'm not sure of the legality of removing stuff from the beach in Hawaii, perhaps Bob as a long time resident can chime in here.><<I'd be checking w/ the State DLNR here. B>>
I would like to buy more live rock, but until I solve this issue I will wait. My water quality is: pH 8.4; Ammonia 0, Nitrite 0, Nitrate 10, Calcium 400, KH 8, Phosphates are .25 ppm.
<The phosphates may become a problem here as an algae fertilizer.>
The only inhabitants in the tank, other than what is in the sand, are about 10 hermit crabs, some snails, some type of eel that was accidentally caught with the sand (boy was that a surprise), some tiny crabs that hitchhiked on my live rock, a couple of interesting sea slugs, a sea urchin, and some sea hares. I target feed the eel, and I drop small pieces of shrimp on the tank bed to feed the crabs. There is never any leftover food on the floor.
<With time you may start hating the crabs, as opportunistic omnivores they may start eating thing they you would prefer they don't.>
So in the last couple of weeks, I have noticed this uniform layer of gray sand, say about the bottom half inch. During my weekly water changes, I stir the sand and I notice there are bubbles that come up from the sand and a smell that comes out of the tank. There is no smell if I don't stir the sand. This layer of sand is most likely hydrogen sulfide buildup, but what can I do about it?
<Increase flow and remove the plenum, they don't really help in my opinion and just make things more difficult.>
It is very unsightly (see pictures) and makes the tank look so dirty. I want to add another couple of inches of sand to the tank, but I don't want to compact this problem even further.
<How deep is it now, it is difficult to determine from the photo?>
Due to the uniformity of the layer, I am almost questioning the construction of the plenum (it came with the tank), and if the layer of screening that was used was appropriate.
<I would not use it at all if possible.>
Most pictures of hydrogen sulfide buildup that I have seen online are spotty patches, not this uniform. Can you give me advice as to how to remove this stuff for good?
<It is determined by the conditions found within the sandbed, more water flow will help create an environment where it is less likely to form.>
My fish are anxiously awaiting the move from the 55 gallon to the 125, but I'd hate to move them if I am going to put them in harm's way.
I reduced the size of the pictures way down so if the quality is too poor, let me know and I will send you larger ones.
<Looks nice.>
Mahalo plenty for any advice you can give, and I appreciate all that you do for us!
Oahu, HI
<Dreaming of Kona...>

Re: Hydrogen Sulfide Issues 6/13/11
Hi Chris,
Thank you for your speedy response, and I apologize for my slow one, I have been a bit under the weather.
<Hope you are feeling better now.>
I am glad to hear that I can accomplish the 20x turnover rate with power heads, for some reason I got it in my head that all of it had to run through the wet/dry. I have already added one Koralia pump rated at 750 gph, and have the Hydor Koralia Magnum 6 on order. I may also get the Koralia with the 425 gallons per hour, just to aim back at the 750 for some turbulent flow.
I will also be removing the plenum this weekend, and adding more sand. Right now, the bed is 3 inches at it's deepest point, so I am lacking there too.
<Yep, best to increase about an inch.>
From what I understand, in Hawaii you can remove rock as long as it is no longer attached to the reef, like it was broken off in a storm or something. As far as the sand goes, I'm not too sure if it is illegal, but we were careful anyway and chose a beach that is more secluded and hopefully just a tad cleaner than others. :)
<Sounds good.>
The phosphates are on the way down, with the weekly water changes I am sure I will get rid of it soon. I did have some brown algae form on the glass (just a little) so I am also hoping this will take care of itself here soon. I'd really rather not start adding chemicals to the tank to get rid of the phosphates, as thus far the only non-natural chemical I've put in there is Prime to condition the water.
Mahalo plenty for your suggestions, I will give them a try and see if I get rid of the H2S. If I have any other questions, I know where to go!
<Good luck.>

Sand Problem, Sandstorm, Moving a sandbed 11/24/10
Hello Crew!
I recently setup a new 175gal (400gal system) bow-front reef aquarium. The live sand I put into the display is too small, getting blown around by my closed-loop system (sand is 1.5" to 2" deep). I was considering (loathing) siphoning the sand out and putting into my 75gal refugium (which has the same sand, about 1", effectively turning it into a DSB).
<As long as it gives you a depth on at least 3.5 inches it might be worth it.>
Being that the system is about 8-months old, generally speaking, wouldn't removing the sand expose/stir-up buried toxins?
<Is an overrated concern in my opinion, especially in a relatively shallow bed like you have.>
Would it be better to do this over 3-4 days while employing a mechanical filter?
<You will create a bit of a sandstorm either way you do it so some mechanical filtration may be useful here. Doing it a little bit at a time might help prevent the sandbed critters from being buried in the new tank
as you increase the sand bed's depth.>
Instead of siphoning, could I put a larger grain of sand on top of the existing sand bed? Or would the larger grain eventually sink?
<It will probably just end up as you are now. Can you not adjust the direction of the outflow for your closed loop so that it effects the sandbed less?>
Thank you!
Re: Sand Problem, Sandstorm, Moving a sandbed 11/24/10
Hi Chris,
Thank you for responding so quickly!
I can't adjust the direction nozzles for the closed-loop system (a mistake I won't repeat in the future). Sounds like I'll be putting in new sand.
Is there a good calculator out there for determining the amount of sand needed for a given depth (2") and tank size (72" x 20")?
<There are a few out there, Google "sandbed calculator" and try a couple, see if their numbers match up.>
Also, I have scores of Super Tongan Nassarius snails in the display and they love to bury themselves in the fine sand. Any idea how large a grain size I can go with them still able to burrow?
<It will still need to be fairly fine, not more than a few millimeters in grain size.>
What's an acceptable depth range for a live deep sand bed?
<4+ inches is what I would shoot for, but it doesn't all need to be live sand, if you can find cheaper dry aragonite for the bulk of the material and only use your existing live sand to seed it with you should be fine.>
Best Regards,
<Happy Thanksgiving>

Replacing a DSB 6/14/10
Hello to all the crew at WWM. Here is a little background on my marine system as well as my dilemma with my deep sand bed.
I have a 90G Oceanic Tech Tank with 30 gallon sump. On the main display, I have a 4" DSB that has been on this system for a little over 2 1/2 years.
My system is over stocked with about 16 fish and 20 + corals, but I more than make up when it comes to filtration. Filtration consists of an AquaC EV 240 skimmer with Mag 18, a 7" DSB in the refugium stage, along with Chaetomorpha and Caulerpa prolifera,
<Mmm, this genus is out of favour... I would pull it entirely>
120 pounds of live rock, 25 watt UV sterilizer, 2 Phosban reactors one containing Rowaphos and the other containing Chemipure carbon. Oh, and for water movement I have 2 Vortech MP40's.
Here is my problem. Recently for the past 3 months or so, I have been getting cyanobacteria growing on the sand bed in patches here and there.
Initially I suspected it was my Spectra pure Max cap 5 stage RO/DI filter that needed the cartridges and RO membrane replaced, so I went ahead and did that. My water parameters are all great with nitrate and phosphates reading zero, calcium and alkalinity are on the money, and my PH is stable at 8.1 to 8.2. My water changes are 20 gallons a week.
I suspect the cyanobacteria is growing because I had been recently disturbing a small section of the sand bed in the front of the glass to eliminate the algae growing on the front glass beneath the sand bed. last night, I moved it a bit again and I began to smell rotten egg coming from the tank. All the corals are fine and the fish as well, but I am concerned about the sand bed and have thought to completely replace it in one shot.
By the way, there are no signs of black areas beneath the sand bed, at least not that I can see on the front or sides of the tank.
Has my sand bed gone bad due to the rotten egg smell and is it a good approach to replace it all in one shot?
<I would try deep cleaning, vacuuming it first... half the front let's say>
How would you all suggest about doing this if it is necessary to do so?
The sand I have in there now is Natures Ocean Bio-Active live sand that is .05mm to 1.7mm in grain size. I plan on replacing it with the same brand of sand, only sugar fine with grain size from .01mm to .05mm. Please help! Any and all suggestions are welcome.
<Please read here: http://wetwebmedia.com/dsbmaint.htm
and the linked files above. Bob Fenner>

Bubbles Under Sand 5/15/10
<Hello Paula>
I see a lot of questions about tiny bubbles in reef systems, but my problem is bubbles under the sand seeming like gas bubbles and a brownish film covering the sand.
My live rock and even seahorses have this film growing on them and this traps the bubbles. Otherwise bubbles are slowly "escaping" out of the sand. I have added hermit crabs, sand sifting star fish and several other creatures to sift the sand to no avail. Can you help??
<Poor water quality for one, Paula. The bubbles you are seeing are hydrogen sulphide gas and can be very dangerous to tank inhabitants. You provide little information as to tank size, filter system, maintenance schedule, etc., so my answer may not be as complete as I would like. A weekly 10% water change is a good place to start, and do use a gravel cleaner type siphon. Doing so will remove detritus and other noxious material. Next step is to increase water flow up to a point where the seahorses are not blowing around/having difficulty swimming. We do not want any dead/stagnant areas in the tank. Gentle flow rates coming from more than one area will give the best results. You mention no use of a protein skimmer, so I highly recommend the use of one. Will greatly help
reduce excess nutrients in the system. I'm going to guess you have a small system for your seahorses so I suggest reading here and related articles/FAQ's shown in the header. http://www.wetwebmedia.com/small.htm
James (Salty Dog)>

Re Bubbles Under Sand 5/15/10 - 5/18/10
<Hello Paula>
Thanks so much for your response.
<You're welcome.>
Actually my system is a 100 gallon open reef in my pet shop with a sump, protein skimmer and two 250 watt metal
halide lights.
<I'm believing this is the shop's show tank.>
We have been having problems with the impeller on the skimmer motor, seems like the problem started with that. We will replace it and see.
<Could very well be without any nutrient/waste export.>
We had a total back up in the system a couple months ago and removed everything including the rocks and most of the water. I syphoned until the sand ran clear and added clean water. This back-up had a really slimy sewer type look to it. Maybe we should remove the sand and replace it.
<I would likely replace in the "show" tank, the system could have been in a state of neglect if this was included in the purchase I see you indicate below.>
In some of our other display tanks we have sand that is not live and they seem to stay much cleaner. Would you recommend new live sand or maybe crushed coral???
<If these tanks are not "show" tanks, I would use no sand/crushed coral at all, just adds to your overhead.>
We lived in Maui for 20 years and always had a reef tank there but we used the ocean water and of course did not have to deal with heaters etc...we are in Oregon now so some of this maintenance is new to us. We bought Noah's Ark Pets and Fish in October. I appreciate all your input.
<Mr. Fenner has put together information regarding the aquatic business and I will provide you a link to the index of this. It may be of some help to you.
<You're welcome. James (Salty Dog)>

Sand Bed Fusing. -- 04/22/10
Hello Bob,
We are getting ready to make the trip down to CT. this weekend and I am looking forward to seeing your talk!
<Ahh! Please do introduce yourselves>
I hope that it is a nice weekend for traveling.
<Me too... Rainy in San Diego, So. Cal. currently>
I have a couple of questions today about a fusing sandbed. In one of my clients aquariums I have noticed recently that the sand is fusing badly along the sides of the aquarium and at the base of the rock structure. It appears to be attached to the structures much to my horror. The tank is an in-wall 110 from Coast To Coast aquariums that is very high in the wall and I don't want to damage it! I understand that this may be a bit of a novice question, but is something that I've only ever had to deal with once before in another aquarium that I service that occurred about 10 years ago. If I remember correctly I simply removed the clumps and it has not been a problem since.
<Shouldn't be. The clumping, clumped-up material is largely chemically and physically inert>
The system runs with a deep sand bed in the display tank. There is a Korallin Ca. reactor on this system that has been running for a few months.
Prior to that a dual-chamber MRC Ca. reactor. Never any problems to my knowledge with the MRC. Shortly after adding the Korallin we had a problem with low pH that coincided with a controller problem.
<Mmm, what/whose media are/were you melting?>
I had the client add liquid dosing preparations for Ca, Alk and Mg. for a period of time until the controller was replaced. Is the cause of the fusing related to possible swings in these levels and pH?
<Likely so>
Of topic (possibly?) before the Ca. reactor this tank had started to develop a problem with Bryopsis. After attempting heavy water changes and frequent changes with large amounts of carbon and GFO along with a large
reduction in the feeding with little positive result, we decided to try high Mg. levels. I had read that some people were having luck with this approach.
<Some have, yes>
It was also mentioned in Lindsay Kayal's talk on Bryopsis at MACNA last year.
<I recall this>
There seemed to be some slight benefit to this, but not sure if it was the Mg. levels that had the impact or just multiple factors. Would the high Mg. have caused the sand to fuse?
Still battling the Bryopsis in this tank and would like to try the Kent Mg. product as many are claiming that it is a contaminant in the Kent product that is causing the success in getting rid of the Bryopsis. I am a little weary to try this given the sand problem.
With all of this is it possible to reverse this problem with the fusing sand or at least to stop it from getting worse?
<Mmm, if you have a "bunch" of clumped material... it might be worth your while economically to "smack it with a hammer" to make smaller bits, rinse it in/with a dilute organic (e.g. vinegar) or inorganic acid for a few days... rinse, air-dry. Will have to be mixed w/ newer/higher Alk. material when used in a biological system later>
I am stuck in a very bad position (will resist obvious the pun here!) with the connection of the fused sand to the rock structure that is very difficult to reach and to a very expensive aquarium. Your thoughts and advice on this would be very much appreciated. Information on this topic has been hard for me to locate, but I am not surprised as I have not seen it in over a decade and I have not heard of many hobbyist's in my area dealing with it.
<There are a few basic types of fused alkaline earth (Ca, Mg mostly) and carbonate, bicarbonate materials that can be formed via the processes you present, relate... All are of limited use as sources of biomineral and alkalinity in the aquarium interest>
As always I thank you very much for your time and for providing the industry/hobby with such a valuable resource in WetWebMedia.
Michael P. Gillespie
<Trying to wake up, recover from last night's wine-imbibing CLHHH campout comm. "meeting", BobF>

Re: Sand Bed Fusing. 4/23/10
Hi Bob,
Thank you for the quick response. We will be sure to introduce ourselves. Going to be getting there early if our travel goes according to plan. I hope that things clear up out your way. When I think of California the
thought of rain never comes to my mind. The only two times that I have been to California was with the Marine Corps for training and it was always dry and hot. Got a sun burn there that left me with scars!
Should the material that is clumped not be attached to the rock and glass?
<Only in extreme cases>
I am almost afraid to put any force on the stuff for fear of breaking the glass.
<A plastic scraper should remove>
The media is Carib-sea large media mixed with the Mg. media NeoMag from Brightwell Aquatics. Will this clumping continue to get worse?
<If the supplementing isn't modified, yes. Do carefully measure and not-over amend... and do pre-mix any/all powdered supplements>
This is such a beautiful system and it is a shame that there are so many problems going on with it right now. I've got to do whatever it takes to shape it up.
I hope that you are well today and fully recovered from the other night's wine sampling and campout, hehe! I am not familiar, what is the CLHHH?
Thanks Again,
Michael P. Gillespie
<Oh, the California Larrikins Hash House Harriers... a drinking/running club of sorts. BobF>

pH Crash After Removing Substrate 7/21/09
Hello all,
<Hi Ben>
I moved my small marine aquarium to a different place in the same room over the weekend. I siphoned most of the water out into clean buckets, and put the fish into one of the buckets along with an airstone. While I had the water and fish out I decided to lower the level of substrate from about 1 1/2 inches of aragonite gravel down to about 1/2 inch, hoping that this would help to alleviate some nuisance algae growth. I filled the tank back up with the same water, less a 5 gallon water change, and when the filters cleared the water up, added the fish back in. The next morning, two of my three fish were dead. I had two clarkii clowns and a yellowtail damsel.
Only the smaller clown survived, and he didn't look too well. The only invert other than live rock is a large Condy anemone (I know - Atlantic - but the clowns hosted in it anyway), and it seemed unaffected.
I ran tests on the water, and the only thing I could come up with was that the pH had fallen from 8.2 down to about 7.9 - I presume because I removed part of the buffer.
<More likely by disturbing the substrate, you released some hydrogen sulphide gas and/or excess nutrients into the water causing it to become a little more acidic.>
I do not have an alkalinity test kit,
<Not good.>
so I don't know what that value is. I suppose there is some small chance that I introduced some sort of contaminant into the system, but I tried to be extra careful to avoid that.
<Yes, likely the hydrogen sulphide. Did you detect a rotten egg odor while removing the substrate?>
To try to recover, I added about 1 1/2 tsp of baking soda on Sunday morning, and a pH reading later in the day showed that the level had risen to 8.0. Meanwhile, the remaining clown seems to be recovering - he ate some food and took up residence in the anemone. As we speak, he's clearing bits of gravel out from under the anemone. This morning, the pH was back down to 7.9.
<Is best to take a pH reading mid-day.>
I did a 5 gallon water change and added 1 1/2 more tsp. of baking soda.
My question is, where do I go from here? Should I add some of the removed substrate back in?
Continue with baking soda? Leave things alone?
<First, you need to get a alkalinity test kit. The dKH is an important parameter to maintain, and without knowing what it is, it would be futile for me to make any suggestions at present. I would not add any more baking soda without knowing what the dKH is.>
My normal water change schedule has been 5 gallons at a time, usually every 4 to 7 days, and it has worked pretty well thus far, other than a bit more algae growth than I'd like. It seems to be mostly Caulerpa, Halimeda, and hair algae. A lighting fixture upgrade some months ago seems to have favored the Caulerpa and killed off most of the hair algae. I was hoping the removal of excess substrate would help the algae situation, along with a recently added powerhead for extra circulation.
<A good protein skimmer would help here.>
Here are tank stats:
Tank: 36x14x12 (30 gallon)
Ammonia: 0
Nitrite: 0
Nitrate: between 0 and 5 ppm
pH: 7.9
Phosphate: 0
Skimmer: AquaC Remora
<OK, you do have a good skimmer.>
Filter/Circulation: HOB power filter with carbon, powerhead
Lighting: 4x39w T5HO, 2 actinic, 2 full spectrum. Actinics: 8am-8pm, Full 9am-7pm.
Livestock: about 40lb live rock, 1 Condylactis anemone, 1 clarkii clown.
Just lost: 1 clarkii clown, 1 yellowtail damsel.
All livestock had been in tank for 1.5 to 2 years prior to this weekend's meltdown.
<Test the water for dKH and adjust, you will likely solve the pH problem.
Read here and related articles in header for help in controlling algae.
Thanks for your help,
<You're welcome. James (Salty Dog)>

Dark spots in newly expanded DSB 6/13/09
Hello DSB Experts!
Thank you very much for your time! I've been reading through your DSB section and it convinced me to add to my existing 3" SB.
I have a 125g tank that's been running for less than two months but some of the liverock etc is from my smaller tank so cycle has been short and uneventful.
I used all new sand. Some Special Reef Grade and some Fine sand.
Then I read about DSBs and added more fine sand on top.
I was trying for only 1/2" but it got so cloudy and in a few areas I got more than 1/2" at a time.
Now it's only been a few days since I completed this and I can see a dark line forming underneath the new sand layer and also see dark patches/circles in places.
<Probably die-off from buried sand dwellers. If you are only seeing this along the glass it may just be algae.>
Some people say that the black/dark patches are an indication of dangerous gas build-up.
Is that true?
<Can be an indication of areas where there is an overabundance of decaying matter and the creation of hydrogen sulfide pockets. However in your case I would give it some time before really worrying about it, will most likely dissipate as long as good husbandry techniques are used. Increased circulation and water changes will help. On a side note more often than not hydrogen sulfide is blamed for tank crashes when the more likely culprit is just poor maintenance.>
Can it really go bad that fast?
<Could if there was a lot of biological material built up in the substrate, which in a new tank is not likely.>
What should I do?
<Water changes and increased circulation should help immensely.>
Thanks for your time!

Re: Dark spots in newly expanded DSB, 6/15/09
Thanks so much. The die off of buried sand dwellers seems like a likely explanation.
I will give it some time.

Clumping sand, calcium deposits everywhere 6/4/09
Hi Guys, my name is Kevin Hooey and I operate a small company out of Toronto
"Total Aquarium Maintenance".
<Ahh! A very nice town... people and fish-wise>
I am confident in my abilities and have
others in Toronto I can turn to for help, but I have a recurring issue that is driving me nuts. I have one aquarium which is a 90 gallon plumbed to the basement with another 90 gallon as a sump. This system has been running for two years or more, and has always clumped sand.
<I see... these are most often a matter of (mis) mix of alkaline and biomineral processes... brought on by supplementation errors, sometimes anomalies of aeration, pH elevation in places>
There is no biotower, there is a very nice bullet skimmer, and a calcium reactor has been added in the last year and a half. The sand clumped before any changes were made.
We use all RO water, with fresh filters and have a 30 gallon refugium which was setup in the last few months. (there was Caulerpa in the sump before, but no sandbed).
<This algae might be involved... glad you're mentioning all>
Sandbed in the fuge and in the tank is roughly 3 inches of sugar sized aragonite.
<And some of this material is so soluble that it too can play a part>
The top layer of sand in the refugium cemented together in about 6 weeks. At the waterline of the aquarium or fuge are large deposits of calcium, and calcium deposits accumulate like crazy within the skimmer and even within the PVC lines. Recently I noticed very little water returning to the aquarium, even though I run a nice Blueline pump as a return. After cutting and draining the line I found a ton of calcium chips, that were blocking the flow.
<Mmm... too much calcium... being precipitated with too much carbonate...>
Calcium has always been between 380 and 450, its been around 400 the past year. DKH is about 12
<At precipitation level>
usually, although I went through an episode last year where it read 20!
<Zounds! Way too high>
Calcium reactor is a fast drip with, a ph effluent of 6.5
(I am using a media which suggests the effluent could be as little as 7.5).
<Too high>
I don't mind turning down the calcium reactor and lowering my values, but this phenomenon happens at such a fast rate that I feel there must be something more extraordinary happening.
What gives?
<Mmm... reads like too easy solubility of the oolite... maybe as well on whatever media is being used on/in and perhaps too high a pH on the calcium reactor, and/or... an imbalance of Mg>
Appreciate the input!
<I propose two experiments... 1) Removing, testing a sample of the present fine substrate. 2) The same for the media in the reactor...
Put some of each in two small tanks, circulate the water... and test for resultant pH, alkalinity, Calcium AND Magnesium... And we'll chat. Bob Fenner>

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