I added some live rock from the LFS a few weeks ago, and one rock had a lot of green algae when I got it - I think it's known as "hair algae" according to what I've been reading. I thought it looked nice in my tank, as it's a very bright green and I thought only brown algae was bad. Now I've read people say that this stuff can take over your whole tank, but mine is not doing that (yet). Should I try to clean it off the one rock or is this alright to have as long as it doesn't spread?