I have some sort of film on top of my 1 gal. beta tank. I clean his tank regularly using only clean glass bowls. No soap, just hot water. Tank has a lid. Any ideas of what it could be?
Any help would be greatly appreciated...

Is this a thick/thin film, does it have a color, is it bubbly or oily looking?
Kae

t's never used for anything else.

I think you misunderstood me. I was asking what the film looked like.
A bubbly film is normal. Male Beta fish make bubble nests. The bubbles soon pop and a foamy film will be left.
If it is an oily looking film than it is pollutants. The break down and decay of old food or fish waste.
If you have any more questions, please let me know and I'll be happy to try and help.
Kae

I have it on my bowl too, it starts right after the fish goes back in!