If you read other reviews that say "It killed my fish" I'm sure it could be due to a lack of research or that they put it in a smaller tank have than it should have. it was. Please don't boil the fish and be smart, use a right size fish tank. I recommend nothing less than 5 gallons anyway. Don't torture the fish thinking the betta should be 1-3 gallons. Position the heater in the corner of the tank vertically, not centered or centered on the floor. You should give the fish a spot where they can stay away from the heat and place the thermometer on the opposite side of the tank (NOT ON THE HEATER) for best results. They will make your little fish happy. I have 2, 1 in each tank. Works well. Great that there is a thermostat. It turns off when temperature is reached, unlike others that stay on.
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