i am not sure if you guys talk about turtles,but i have a 40 gallon tank and there seems to be a film on top of the water makes it look like a rainbow is there anyways to fix it and is it harmful to the turtle??
Does your filter break the surface of the water? The film is most likely oils from the proteins in your food, and without a source of surface skimming or water agitation the film becomes really obvious.