It's green. It looks like little balls of short hair. I tried plucking it at first, but it's getting worse. I've done to many things different recently to tell what caused it. I changed to Oceanic Salt, but it's been a while since that, I'm trying some new food (I didn't check for phosphates, I guess I need to do that), I started using a new water source a few months ago. I bought an RO/DI unit, instead of buying distilled. Lets see what else...I guess that's about it. Oh wait I started using Kents Phytoplex.