Compared to rim-mount heaters, submersible heaters offer accuracy (±1 ºF vs. ±3 ºF), safety, tamper resistance, and greater versatility in placement. A directly adjustable control stem allows you to dial in the temperature setting you want. Limiting stops prevent accidental adjustments to extremely low or high temperatures. Internal and external seals provide outstanding protection from leakage. The wire-coil heating element is double-encased in tubular glass supports-safe and lightweight. A power lamp indicates on and off cycles.Engineered for either fresh- or saltwater aquariums with an operating range of 18-32 ºC (65-89 ºF). Supplied with two secure suction mounting clamps. Powered by 115 V AC. Select the proper wattage for your size aquarium, allowing a minimum of five watts per gallon.