help!! For the last couple of months, my betta's 5 gallon tank keeps getting a thick waxy coating on the top. I clean it weekly, w/gravel vacs. It's heated, no filter. He's alone in the tank. It's so gross, I net it out and it comes right back again! I have plastic wrap over 3/4 of the top of his tank to keep the warmth in, but it started months after that. I've been treating him regularly w/medication. As soon as I stop the meds, within a few weeks, it's back! He has red spots on his face and looks scales and raggy fins again. This is soooo frustrating! He's on meds more than he's off them!