How To Warm Water For Betta Fish. Place a heater outside or in your fish tank. Close it with its cap and let it float on the surface of your betta fish tank.
Wrap your tank in towels or anything that will keep warmth in or an electric blanket. The water temperature must remain moderately warm at all times. Use a water conditioner available at pet supply stores to remove chlorine and other harmful substances from the fresh water.
Replace the hot water as needed.
The water temperature must remain moderately warm at. Cutting straight to the answer you are most likely looking for the ideal water temperature for betta fish is between 78 and 80 Fahrenheit 255 and 265 Celsius. If it is hard for you to do so due to the small tank or other reasons gently bring the fish out of the tank let them stay in a bucket of water. Bettas still need warm water even at night so rooms that cool down overnight will not work.