Substrate Depth question

[greatpratty]

Hello, I was wondering what everyone's opinion on substrate depth was. I have the conciencious(sp) marine aquarist book and it talks about a good sand depth should be 1 - 2 inches but my local fish store recommends as little substrate as possible. On there recommendation I have removed much of my sand as to only have 1/2 - 1 inch of sand.

The reason I am asking is that I am concerned about nitrate buildup and would like to keep the lowest level of nitrates as possible. Some say that a deeper bed will produce more nitrates and others say that a deeper sand bed reduces nitrates.

What do you recommend to reduce the buildup of Nitrates?
Thank you for your help.

 

[DeputyChiefJR]

Like most LFSs, they're full of it...Substrate provides a home for loads of beneficial bacteria....Really an inch should be the minimum, IMO...1-2 in an unplanted tank and 2+ in a planted tank...Do these guys all go to one idiot course before they get hired or is it part of the LFS training?? All it means is you might have to clean a bit more but it sounds like they're just giving you a free excuse not to do water changes...

 

[Fishieness]

a 4" deep sand bed would be great :thm:

 

[Owens187]

a DSB (deep sand bed) does not usually add nitrates, as long as its 4" deep or more. if you look in fenners book again, he also calls a deep sand bed a nitrate reduction bed. you usually want 2" or less, or 4" or more. i personally use 5" of aragonite live sand in my reef, and 2" of plain aragonite in my FOWLR, and along with the live rock, i have NEVER had a nitrate problem.

 

[Lorna]

I currently have 5" of aragonite which my sand gobie has redistributed on a regular basis to 6-7 inches in some places to 3-4 in others.......if going with a dsb make sure that you introduce enough inverts that will stir it up and make sure stir the top couple of inches in a rotation reguarily just don't go too deep to disturb the denitrification bed. Between my gobie, sea cucumber and nassarius snails my dsb is turned and stirred (not shaken) regularily. Don't add a sand sifting starfish as these will eat everything of value in that sand bed you are cultivating.

 

[greatpratty]

Ok, thank you for the replies. Is it fairly normal for nitrates to build up over time or if you have the proper depth sand bed will you nitrates stay low? My nitrates hover between 20-30 ppm and I am doing water changes every two weeks. Does this sound normal. It seems that I have read that some tanks do not build up nitrates.
Thank you.

 

[gomrjoe]

I have read about the same problem, and am experiencing it myself. It is called old tank syndrome. Supposedly by using additives or LSB, live sand boosters it helps, I have tried adding StressZyme, and it hasn't done anything. I too do bi-weekly 15% water changes religously, and my nitrates go back up to 20 ppm.

I read earlier in this thread about sand sifting stars not being beneficial, is that really true? My LFS told me that they helped stir up the sand bed and would be extremely beneficial, especially for the buildup of detritus. Not that my LFS is gods gift to marine tanks though, they could have gone to that same marine tanks for dummies class!

What is/are everyones thoughts or experience with sand sifting stars?? It would be a shame if they are bad, I have three of them, and my 2 year old daughter loves them! :help:

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100 gal
2 percs
1 pac blue tang
1 yellow tang
1 diamond watchman gobie
1 coral beauty
1 firefish
1 bubble coral
1 star polyp
1 colony of pulsing xenia
cleanup crew: hermit crabs, turbos, emerald crab, sand sifting stars

 

[Lorna]

Sand sifting stars will decimate the life that is in the sand bed eating everything that is beneficial to your bed and in fact over time by eating the life it renders it basically dead. You should remove the stars and get some inverts that only stir the top layer and let the dsb do its work below that. my bed is full of gas bubbles that bubble to the top and I know it is working these bubbles are nitrogen that is released and that is why I know it is working as it should, the nitrate is converted to nitrogen in the dsb. I have no nitrate problem, if you still have problems check and ensure that the nitrates are not the result of overfeeding or overstocking????

 

[Zoolander]

From what I have been reading, 3" is what other sites are calling the ideal amount. The only problem I can see with that is people with tanks smaller than 20 gallons lose a lot of space with three inches dedicated to just substrate. The best thing I have read so far is 30lbs for a 10G and 45lbs for a 20G. That is what I went off of for my 10 that I am setting up. I was also debating putting another 10lbs or so of live sand on top of that or maybe just adding 20lbs of aragonite and then 10lbs of live sand.

 

[mysis]

Don't add a sand sifting starfish as these will eat everything of value in that sand bed you are cultivating.

you can add 1 starfish per meter squared, and the DSB will still be healthy.