Hi everyone, I'm new, so please speak slowly and carefully

. I have one male betta fish in a 5.5 gallon tank with a heater and filter, and feed him three pellets in the morning and three at night. As of lately, I've been noticing this weird filmy stuff that develops on the surface of the water. When I drag my finger through it, I get white stuff all over my finger. It doesn't seem to be affecting my fish, but it looks nasty and I'd rather not have it in there. Any ideas on what it is and how to get rid of it?