We have a Betta as well and never have this problem either. What kind of water are you using because that could be the cause? I would suggest going to the store and buying bottled water instead of using tap water if you are using tap water now. The 1 gallon milk jugs of natural spring water are what you should look for. We don't use a tablet, but we do have some drops that we put in the water. Also as others have said DO NOT put anthing else in that tank with the beta or it will continue to attack it until one of them is dead. There is a very good reason they call them fighting fish. Good luck.