<a href=showthread.php?s=&postid=13009329#post13009329 target=_blank>Originally posted</a> by Sk8r
It's also nitrates. Which may come in via tapwater.
basically it's not algae at all, but bacteria, and it feeds off CO2, light, and water. It will also take in nitrates, phosphates, etc...pretty much an 'anything' kind of nuisance. There is one thing you can deprive it of that will slow it down: light. Turn your lights out for 3 days (4th actinic if you're mh)---but there's a catch. If you get a big dieoff of the stuff and don't have a powerful enough skimmer you can crash your tank. Your skimmer's potency is one of the big things that helps get rid of this stuff's dieoff.