I'm actually having the same problem, in a 10 gal with a betta. He doesn't seem to notice it at this point, and I think I'm gonna put him in a bowl for a few days. (I also have never bothered to run tests, mostly due to the fact that I have a betta in 10 gallons. Yes, I'm irresponsible. ;__; ) If I tear the tank down, and then blackout, do you think I can get rid of most of it without antibiotics?
I've also heard elodea is good for some type of prevention, but I've never had this kinda of outbreak before.