Black spot in sandbed

[lonbrat]

I have a 10 gal. Salt water and sand basically. With a few rocks lol
I used to use it as a nano of sorts but since I upgraded I just left it running for a few months, adding water etc. Almost as a pod tank.

I just recently came back around to looking at it, removed tons of algae, checked water etc. And noticed a really big black spot in my sandbed, against the glass? I was thinking about keeping some sexy shrimp and maybe a rock nem in there, but I wouldn't want to kill them with scary stuff under the sand lol
It's only about 1-2 inches deep any ideas on what this is?
Thanks!

 

[cloak]

It might be a pocket of Hydrogen Sulfide.

http://reefkeeping.com/issues/2005-12/rhf/index.php

 

[shellz]

It sounds like a form of algae, I have seen that in my LFS. Just combat it like you would normally do for unwanted algae

 

[RayAllen3422]

Any pics?

 

[lonbrat]

Any pics?

If I had to guess what caused it,I'd guess that a snail went down there and died?

 

[CStrickland]

Yikes!
Don't poke it!
Read the article cloak linked to. You need to handle it properly so as not to release too much toxins.

 

[RayAllen3422]

Yeah. That must have been a giant snail.

 

[lonbrat]

Lol well since it was only 10 gal. I think I'm just going to suck all the sand out and clean it up, starting over.

( plus I kind of wanted to get rid of unsightly algae anyways lolol)

Also that was just a guess with the snail, maybe 10 died xD I think that spots been there a while though lol