What is this and how do i eradicate it? Im thinking i could be a form of hair algea but want to get some other opinions first. I have scrubbed it off with a tooth brush, sucked it up and done water changes and it comes back in a couple days. Also what is on the sand? The tank is 3 years old so i dont think it's diatoms but i could be wrong. I know i have something called flatworms (well i was told by lfs that's what it is) It's small square rust color things all over the rocks and sometimes glass, so could this be what's on the sand? I've been sucking them out with an air line tubing and it seems to be slowly working. But any tips would be appreciated. So questions are, whats the green slim looking stuff on my rocks and brown stuff on the sand?