I have my first Betta. I have a two gallon tank with a heater that is keeping the water at 80. When I go to change the water, how much should I take out. Also, can I microwave the new water so it will be at 80 before adding it? Or should I put him in a bag with his old water and let it float in the new water before releasing him. I'm using purified drinking water. Thanks for the help.