A friend of mine decided to start a salt tank. I hadn't gone to visit in a while, and she REALLY let her tank go.

She has this white fungus, for lack of a better word. She still has fish living in the toxic mess that is her water, so my challenge is this. Is there a way to help fix the problem?
I've mixed up a good sized batch of new water and will do a massive water change to start with. Every surface is covered in this nasty white filmy stuff, so I have removed all objects from the tank. I'm strying to syphon out as much debris as possible, but the white film just won't come out. As the rocks are really gross I will have to rinse in hot water and scrub. I'm open to suggestions if anyone has any further words of advice. . .
I guess that if the tank cycles again and she loses her fish, it'll be easy to convince her to either leave the hobby or become a more scrupulous fish keeper.