white scum

Question
I have asked several 'experts' but none can give me a decent answer.hopefully you can. I bought a betta for my office as they are low maintenance-no heater or filter required. He is in a small tank. I keep having to remove a layer of white scum off the top of the water every couple days. What is this stuff? I remove water and add water weekly,and twice I have changed all the water and sterilized the tank. That helped for a while but then the problem returned. Is the fish itself producing this scum? The other experts say to get a filter,heater... Duh-I got this type of fish because its supposed to be LOW maintenance. What gives?"

Answer
Low maintainance is a matter of opinion. A bicycle can get you from home to your office in a low maintainance way. How much stuff would you ever need to fix on a bicycle. but it can be a lot of work.
  Respectfully, did you ever have a goldfish in a bowl when you were a kid? There is only so much oxygen in the water. You have been changing water but most of the microbes stay. That little goldfish in the bowl never lived long. Bettas are short lived fish. 30 months in the wild.
The white scum is made of protein. Left over from dead microbes that cling to the glass when you take the water out. Which is why when you sterilzed the tank it got better. You killed them all.
 Low maintainance can mean less equipment to worry about OR less equipment to help you. Since you want a small tank in the office I suggest one of those "ALL IN ONE" tanks. They come with everything built in. You will need to change filter material. But it would be less worry than you have now. They come in nifty colors.
  Otherwise I wonder is this YOUR office? If it is are you allowed a bigger tank? in most things smaller means less work. In the aquarium world there is one thing that is true....BIGGER IS BETTER. BIGGER IS LESS WORK.