If he's living in a bowl (which I assume is unheated) he probably wasn't doing very well to begin with. 65 degrees fahrenheit is much too cold for a betta, they need something in the vicinity of 75-82 degrees to thrive.
Also, you need to treat any water going into the tank with a dechlorinator. Chlorine and chloramine are all found in domestic water supplies, and can kill or seriously harm your betta fish. I would suggest reading a few threads around here and taking the time to do some research before going out and purchasing another fish if that is your intention.
Forgot to add, in a bowl that is a gallon or less, you should be doing daily 100% water changes. Even if your water looks crystal clear, all the harmful things like ammonia and nitrite, are also invisible and so you can only tell through testing the water (I highly recommend purchasing the API liquid test kit) and observing your fish's general behaviour.
Last edited by LittleBettaFish; 01-16-2011 at 03:03 PM.