blue Gravel

[Tazman12]

Hi guys I have a 30 gallon tank. with Various small community fish
Mostly tetras of various type.

I have blue gravel in the bottom about 2 inches worth. I have noticed that some areas of the gravel a becoming black on the tops.

does anyone have any idea what may be causing this.

My nitrite levels are at zero and the tank is about 4 months old now.

Thanks for your help

 

[Zak Ursulo]

I can think of 2 things right off the bat.

1. the paint is coming off the gravel. (if its painted that is)

2. algee is growing on it.

<edit>

There is another possiblity that i can think of but i dont know much about it. In sand you can get "dead zones" im sure someone here knows more about that than me.

 

[Nix]

Theres a good chance it is alagea or paint fading, I have blue gravel in my 10 gallon and the paint is begging to fade and the rocks are turning white.. uhhg

 

[BlueAngel]

I would say it's algae growing on the rocks.

 

[JAYJT]

I reckon its algae growing on it mate, use a gravel hoover once a week, i do and it solved the problem for me

 

[Tazman12]

I just added 4 little Ottos today will that help any.

I will also siffon once a week

thanks