white cotton- like growth on aquarium rocks

Question
Hi-

I was wondering if you might be able to help me out. I just recently cleaned my 10 gallon fish tank out this weekend, and I noticed that there was white cotton - like growth on the aquarium rocks. (It looks like cotton floating on the top of the rocks) I was wondering if you knew what this might could possibly be? I just bought a guppy from the pet store this weekend & added it to the tank after the tank was cleaned. Do you think the fish could possibly be sick, or might the white cotton - like growth on the aquarium rocks be fish eggs? Thanks!  

Answer
Hello,

Is the only thing you have in your tank guppies? Because guppies are live bearers so they don't lay eggs.

White cotton is usually a sign of fungus, but fungus usually grows on the fish, not on the rocks. However, you shouldn't take the risk that it isn't fungus, as it could spread to your fish. I think you should add an anti fungal to your tank right away. Pimafix is a good one.

I hope this helps,

Good-luck,
From Stephanie