What Is This?

[TekFish]

There's this stuff, scum floating around on the top of my water, but I'm not sure what it is.
I have Java Fern, Anubias and Amazon Sword.
We had some other plants but they died, we didn't take them out for a while because we thought they were 'melting' like crypts so I think the film is plant residue.
Help?

TekFish