Gunk on my rocks!!

[Julianna]

I am cycling a new 39 gallon fresh water tank fishlessly. The tank is set up with standard gravel and flourite, as well as some "sponge rock" I bought at the LFS. It was dry and in crates when I bought it, and the store employee told me it was perfectly safe in a fresh water tank. I brought it home and boiled it for 20 minutes. Then I set up the tank and filled it. There is nothing otherwise alive in this tank yet. The rocks, however have moldy looking white gunk growing on them and yellowish stuff, too. What is it! Can it hurt fish!! Should I remove it from the tank!!
Julie

[OrionGirl]

Sounds like a slime algae or mold. Usually not harmful, some are lovely colors. You can remove the rock and scrub this stuff off, since it may take over the tank if provided the oppurtunity. I have some in my planted 40, and it stays just under the substrate on one side. Never caused me a problem, but I seldom have tons of excess nutrients in this tank.

[Julianna]

Thank you for your quick reply. I think I will try to scrub it off, since I've barely gotten started and it's already got a good hold!!
Thanks again!! Julie