I have a Betta in a 4-gallon "tank" (a small animal carrier that holds 4 gallon of water bc he decided to be crazy territorial and flare up at all filters) with a TopFin Betta heater. Today I noticed all across the top of the water is oily (rainbow) looking. Could this be because of the heater???? It's really the only thing that would make sense bc its the only thing that oil would possibly come from. It's been in there for maybe 2 months now and the only difference in those 2 months is that I put the tank under a desk light, which is a good 3 feet above the actual tank so I highly doubt that's the issue. Should I take him out? I don't want to hurt him by keeping him in oily water but I don't want him to get hurt from touching it when I take him out. Then wouldn't have him in a tank with a heater for a while since I don't have tons of time this week to go to PetSmart. Should I just do that and have him in an unheated tank and get a different type/brand of heater asap?