The Hydor Betta Bowl Slim Fish Tank Heater helps to create a more livable environment for your betas， glow fish， reptiles and other finned friends. The heater promotes an ideal water temperature. It features a Positive Thermal Coefficient element to heat the temperature of the water an average of 5 to 10 degrees warmer than room temp. It’s perfect for glass， plastic and acrylic tanks and is safe for use under gravel. There’s no temperature to set， and the slim heater can be used in fresh and saltwater environments. It’s easy to hide and takes up minimal room.