Originally Posted by cpbirds407
Thanks guys! Very helpful... but I still don't know what causes it.
Lemme see what I remember... I'll look it up for you later but, it's an in between stage of decomposion between ammonia and nitrate. The "protein" molecule is half attracted to air and half attracted to water, which is why it floats, and why so many protein skimmers use air bubbles to function. You can syphon it out, you can tupperware remove it, but it will always come back.
A good efficient skimmer will keep it at bay for you, and if your skimmer is "rated" for more gallons than you have, it either isn't working, of it's bad quality or they flat out lied about it's rating.