It's a bit big. I have it in a 2.5 liter tank. Heaters in the store cooked my Betta! The Betta needs a programmable heater to keep it at 78. Set this heater to 77 and it will bring the water up to around 77.5 which is perfect for your little friend. I gave him a few days in the aquarium with a thermometer in the water. This is exactly what gave me confidence BEFORE I added my friend to his tank.
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