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Amazon.com: Hydor Betta Bowl Slim Fish Tank Heater, 7.5-watt, measures 3.5 inches round, black; For tanks 2-5 gallons : Pet Supplies
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Amazon.com: PULACO 25W Small Aquarium Betta Heater with Free Thermometer Strip, Under 6 Gallon Fish Tanks (Preset Temperature 78℉) : Pet Supplies
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