hitop 50w 100w 300w non-glass adjustable aquarium heater, fish tank heater thermostat 10 20 50 gallon, submersible fish heater for turtle tank betta fish (50watt) hitop <p>size:</p> <p>50w: recommended for aquariums up to 15 gallons.</p> <p>100w: recommended for aquariums 10 – 30 gallons.</p> <p>300w: recommended for aquariums 30 – 50 gallons.</p> <p>be sureto purchase the correct heater for your fish tank, buying a heater too smallfor your tank can cause under heating.</p>