Fungus on my tank?

[Penguin]

I have a twenty tall with four Danios in it. I used to have 2 rams, and a 3 guppies as well. However a while ago the rams got ich, and didn't make it. Afterward my tank got a white fungus that killed the guppies. One of the Danios got it, but recovered nicely. However it didn't just infect my fish, but the tank walls and plastic plants as well. I've washed the plants totally in hot water and scrubbed the tank during a water change as best I could. Although it really helped, I still have some and it's getting to be a problem again. I've been using Pimafix which worked wonders for my fish, but hasn't done anything for the fungus still on the walls and plants.

Does anyone know what this is or how to get rid of it? It almost looks like little snowflakes, but grows into strings when there is enough of it. I do regular water changes, about every week or other week.