Marineland Visi-Therm Heater 25 Watt 25Watt &#045; 5 gallon tank 50Watt &#045; 5&#045;20 gallon tanks 75Watt &#045; 5&#045;25 gallon tanks 100Watt &#045; 10&#045;40 gallon tanks 150Watt &#045; 20&#045;50 gallon tanks