What is this growing in my tank

[swendingo]

hello,

a few months ago my friend was moving out of the country and gave me a really good deal on his entire tank setup. so we moved the whole thing from his house to mine. I am very much a novice and have been trying to read up but there is a lot of information out there.

I have little things growing all over my rocks. I was hoping that someone over here could help me identify and let me know whether it is something I have to treat or just live with.

[D12monkey]

That's a form of sponge/tunicate. It's completely harmless and is a sign that the tank is in good shape.