Marineland - VisiTherm Submersible Aquarium Heater. 400W. For years, the name "VisiTherm" has been the industry standard for excellence in aquarium heater performance and reliability. Now, there is the VisiTherm Deluxe, an advanced design submersible aquarium heater that constitutes the next important step in aquarium heating technology. Water calibrated to ensure precise temperature selection and superior performance, the VisiTherm Deluxe delivers the ultimate in direct-set control, compact double sealed durability and certified accuracy to within one degree. With a simple "click" of the dial, you choose the ideal water temperature. The custom DoubleSuction Mounting Bracket features an adjustable three-position window that ensures easy-to-view temperature setting. And, of course, every VisiTherm Deluxe is CSA listed, designed to precise standards for extended submersion and operational safety. It is available in 25, 50, 75, 100, 150, 200, 250 & 300 watt sizes. 25Watt - 5 gallon tank. 50Watt - 5-20 gallon tanks. 75Watt - 5-25 gallon tanks. 100Watt - 10-40 gallon tanks. 150Watt - 20-50 gallon tanks. 200Watt - 25-65 gallon tanks. 250Watt - 50+ gallon tanks. 300Watt - 55+ gallon tanks.