-pushes Erica- listen to her- she gave lots of good info...

but it sounds like the main reason your bettas -may- be dying is that you're not dechlorinating. make sure that ALL water you put in your betta's tank is dechlorinated. if your water is not dechlorinated, it will lead to the quick demise of your betta. Yes, tap water DOES have chlorine in it, so make sure to use stress coat if you must use tap. [pretty sure Erica explained the stress coat thing]

I agree with many of the people who have posted in this thread - make sure you keep your betta in a one gallon bowl, at the very least.

good luck!