It's algae. I get three types of algae at the moment because my lighting sucks and I don't have a timer. I get Hair Algae by my filter and Hard "green dot" algae on the wall of my tank right under my light. I just can't win. T_T
The floaty algae you see is brown algae. it only happens in tanks that aren't fully established. I saw it alot when I was cycling my tank towards the end of the ammonia peak to nitrITE step. Water changes clean it up. I also noticed a stlight decrease in my brown algae when I started floating IAL in my water. But I don't know if that's just a coincedence.
I would get a timer and better lighting, but I don't have the money yet. It isn't harmful to my fish so I just remove it about once a week. If the floaty pieces get really big on me, then I suck them out of the tank with a turkey baster. It figures that the moment you make a tank healthy for fish you make it healthy for every type of algae on the plant. XD
Here's the link
for a quick overveiw. I'm still looking for a really good site about algae. If you look at my other post complaining about algae you may see different links from this one.