RBA

My 10 gallon tank is going thru a nitrogen cycle for last 2 weeks. Amonia is decreasing and nitrite is increasing. Suddenly i noticed that the stone that i have in the middle of the aquarium is changing its color or the top part of the stone is turning dark brown from its original color of very light brown. Botton part of the rock is ok but just the top parts are dark brown. Does anyone know whats happening. I have only 2 danios in my tank and 4 plastic plants. I havent changed water for almost 3 weeks and i feed the fish only once a day. Please Help

vin

It sounds like you are developing what are known as Diatoms. These are tiny marine organisms that are related to aglae...They are perfectly normal for new aquariums and are perfectly harmless. They may go away on their own or you can get a couple of Otocinclus catfish that would love to snack on them. Wait until after you're cycled to add any more fish though...Especially otos as they are sensitive to water conditions...

You should do partial water changes throughout your cycle, but do not vacuum the gravel as this would eliminate the beneficial bacteria you are trying to colonize...But a 2-3 gallon water change won't hurt.

Shelby

One other explanation You didn't say what kind of stone you have. Lava Rock will darken as it becomes water logged. Sounds normal to me.

darkwolf29a

I would ask what rock it is. Some is good for aquarium, some aren't, and I have heard bad stories about the lava rock.

COBettaCouple

the diatoms can be wiped off easily for the most part and do just affect the look of the aquarium. Otos go to town on the stuff like vin said but are sensitive fish, especially their first month in the tank.