Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
The fuzz is fungus. Fungus lives on things that were once living. Dead fish, fallen food and so on. In most tanks there is not a lot of fungus, so you do not really notice it. But when they get a large source of food (dead fish) the fungus multiply. Then there was more food (from the fungus point of view) and a lot of fungus spores to take advantage of it. So the algae wafer grew fungus.
Ditto the above: A good water change will reduce the fungus population in the tank, no need to treat with anything.