# black stuff in sand



## Fish rookie (May 21, 2012)

Hi,
I notice thatthere are some black looking stuff in the sand but they are not algae. I read some books and one said nitrate built up can do that.
I am not sure if I should take out the plants and scope the sand out as I am worried the black stuff might be bad for the axo in the tank 9also worry about hydrogen sulphite release).
So far, no one in the tank seems affected.
It is my axolotl tank, 1 axo, 25 gallon, with about 10 ghost shrimps. We dont feed the shrimps, the axo gets dry pellets once a day or once every 2 days. Water chnage twice a week. Rena XP1 filter. No Co2, no excel, some ferts.
I have put some jobber root spikes in the sand before, not sure if they are the cause of this. Some root spikes have come up (I can see some white crushed powdry stuff around the roots of some plants) but no one seems to have been affected.
It is a low tech tank and does not have much current. It has a lot of slow growing plants.
It is hard to show the black stuff they are like in the middle between the bottom and the top, look like dark patches, really black.
My sand is about 3.5"-4" think on the back and may be 1-2" in the front...is it because it is too thick and has no oxygen so the ammonia cannot be converted?
It is pool filter sand.
Thank you.


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## Sploosh (Nov 19, 2012)

I noticed the same black stuff in the sand in my 10G invert only tank - the sand was half the tank, 3-4"deep. That tank ended up having a mass die-off due to solid waste buildup/too high nitrates. I believe it was due to the deep sand - I could be wrong about that though.
When I pulled the sand out of the tank - some of it was really black - stained almost.
Although that tank had 200+ shrimps, 20+- cpos, 200+- snails. Not sure how much waste 10 ghost shrimps and 1 axolotl will create.


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## Fish rookie (May 21, 2012)

Thanks for the reply.
I dont use activated carbon, only purigen, so it is probably not that. Howver, now that I think about it, I did have carbon inthe filter in the beginning and I did notice that there wrre some black powder in the filter floss when I cleaned up the media, so that could be it.
I also suspect the thick sand might have something to do with it. I will wait and see. 
They dont produce lots of waste at all (a recommended tank size for an axo is 10 gallon and this is a 25 gallon), and I chnage my water (30%) every 3 days. I suspect if there is a nitrate built up under the sand it is from the root tabs I placed.
I do not have a high nitrate reading at all, it is under 10. I need to dose some N in my water column from time to time for the plants as the N is very low otherwise.
I read a book that talks about this and the author said I should not disturb the sand that has turned black. The ammonia built up will slowly come up to the surface, the surface of the sand has oxygen which would allow them to be converted by bacteria, same applies to H2S that they should not be disturbed. Is this true?
I can also remove the plants, took out those sands then refill sands and replant the plants.
So far, no one seems to be affected. It could also be the carbon powder as suggested, too. 
Has anyone has any experience in this regard?


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## jbyoung00008 (May 16, 2011)

I get similiar build ups of whatever it is in all my tanks along the front glass Mine is usually brown not black. Stir up the substrate in those areas. Problem solved. If you are really concerned after you stir up the substrate do a water change. Digging up the plants to remove it will do more harm to the plants than good. Maybe take a gravel Vac and vacuum those areas if you are really worried it will cause harm to the tank. Having deep substrate does seem to promote these dark spots.


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## Fish rookie (May 21, 2012)

I sucked out some sand today and they were very stinky. Whatever is underneath is nasty. I did about 60% wc.
The sand is much thinner now. I really should nto have put jobbers root spikes in there, think they have something to do with it, and they have not even dissolved after al these time!.
Thanks for all your help guys.


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## jobber (May 14, 2010)

Did I ever give you root spikes?


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## Fish rookie (May 21, 2012)

No it was some root spkies I got from Ronas. LOL
Not meant for aquarium, just for terrastial plants.


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## Flear (Dec 8, 2012)

black looking stuff, ...

initial thoughts are hydrogen sulphide.
produced at depths in the substrate that are oxygen deprived after nitrates have been reduced to N2
next is H2S, hydrogen sulphide.
please don't disturb this, your asking to kill your fish.

next thought, is the black stuff granular at all, not H2S

H2S, evidenced by a coating plastered to the sand smells lie rotten eggs i hear, can kill your fish in the time it takes to catch your breath.
is a problem if you significantly disturb the sand bed to release it directly into the water column, otherwise diffusion into the water column is slow enough its neutralized before any harm is done

there are no test kits for H2S in the hobby that i know of currently

yes the common answer about H2S is it will kill your fish
the not so common knowledge is this is only a concern when disturbing the sand bed enough to bring it directly into the water column

adjust your sand bed depth according to if you tinker with your plant layout or not
deeper if you don't, 2-3" max if you do
3"+ considered a DSB, don't tinker with the sand bed & it's got a lifespan, 3-5 years, 2-3 + years no water changes needed, just top up your tank


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## Fish rookie (May 21, 2012)

I sucked out lots of the sand, they really stinked.
The sand bed is now much thinner.
There were lots of black sand under a peice of wood. I think those were caused by waste trapped underneath. I am 99% sure they were H2S.


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