So I have one small little female betta in a 1 gallon plastic bowl. She has been in there for awhile but now Im starting to notice that there is a slimey substance on the top of her water. I thought at first it must be because she was in plastic and the plastic might have melted into the water or something. So I switched her into a 1 gallon glass bowl. I didnt see any of the slimey stuff anymore until this morning. All she has in their is some gravel, a heater and a mini cave like thing. IDK wat it is...any ideas??