Please fill this out! :)
What size is your tank?
What temperature is your tank?
Does your tank have a filter?
Does your tank have an air stone or other type of aeration?
Is your tank heated?
What tank mates does your betta fish live with?
What type of food do you feed your betta fish?
How often do you feed your betta fish?
How often do you perform a water change?
What percentage of the water do you change when you perform a water change?
What type of additives do you add to the water when you perform a water change?
Have you tested your water? If so, what are the following parameters?
Symptoms and Treatment
How has your betta fish's appearance changed?
How has your betta fish's behavior changed?
When did you start noticing the symptoms?
Have you started treating your fish? If so, how?
Does your fish have any history of being ill?
How old is your fish (approximately)?
I would do a 100% water change, try to get whatever is in the water OUT! Whenever something looks wrong with one of my bettas, I always change the water. That will often help a lot. Also, the film that you are seeing on top, oh, I know this! I want to say that it is just buildup, and I think that there is a thread for it somewhere, but alas I cannot find it XD. I won't hurt him, however. I would do a 100% water change and fill out the questionarre and then we can see what we can do for your little guy! :)