White Fluff Found Floating In The Tank

[out_of_eden]

I noticed today that there are several small pieces of white fluff floating throughout the tank. it may be rotted flake food, but it's a lot and i never noticed it before. Does anyone have any idea what this may be and what I should do about it?

I have a 50 gallon tank with 1 swordtail and 4 platys and am expecting platy fry soon.

Thanks for your help,

Helen