black spots in the sand

[thekarens]

I've noticed a couple spots in my pool filter sand have turned black. I'm wondering if that's the normal diatom bloom of a tank that is cycling? I don't "think" its anarobic (sp) because it's at the top instead of the middle or bottom. So far parameters are still fine, but wanted to get opinions before I do have issues.

[cichlid1409]

I had noticed something like that awhile back i just siphoned it up and it hasn't ever come back. I dont really know what it was but it looked nasty so it left my tank asap.

[nacra99]

Hmmm..perhaps a pic would help.

If you are still cycling and its growing on the glass and everything else, and upon closer inspection it looks brown rather than black, it's most probably a diatomic bloom. (no biggie)
If it attached itself to the sand and is fuzzy then it might be black beard algae. (no biggie)
If it is slimy and seems to spread and "crawl" up glass it's Cyanobacteria. (BIG Biggie - let us know if you have this)

[thekarens]

Its like the sand has turned black. Its small spots. No fuzz or slime. Its only on the sand.

[nacra99]

hmmm... very strange.... the only thing i can come up with is diatom growth.

[Somefishguy]

has happened to me, but slightly under the surface... like a few mm under... I just vaccum it up

[imagirlgeek]

When you stir that area, do bubbles come up? Poo and food will settle in the sand and decompose. If you don't stir it occasionally, pockets of gas will get trapped and can become toxic. Churning the sand and releasing the gas will keep it from hurting the fish. I just run my fingers through it every once in a while and never have had a problem.

[Zulaab]

+1 for imagirlgeek. The bubbles are toxic to fish. You are running the same problem I have. I have to much sand in the tank and it allows for decomposed material to be compressed and at this point when bacteria gets to it gas pockets form..

[thekarens]

I've stirred it or shoved the python down into it and nothing has come up but I'm just going to keep stirring it when I find those spots.

[Zulaab]

I've stirred it or shoved the python down into it and nothing has come up but I'm just going to keep stirring it when I find those spots.

This is why I am hoping to con someone over to help me very soon redo my big tank.. I have to much sand in my tank, and it allows for the gas build up which will in turn, turn the sand black from the bacteria eating at the gas and organic material in the sand. Run no more than about a 1" layer and you will be fine. Right now I have 2-3 up to 4 inches where the fish have moved sand... and I need to cut it down...

[eklikewhoa]

Like Jesper said... it's bacteria, like cyano.