Uniclife Aquarium Heater Preset Submersible with Electronic Thermostat for 10/20/60/80 Gallon Fish Tank Heater 50W/100W/250W5~20 gallons fish tanks were recommended. Applicable for freshwater, marine and tropical aquariums. Preset temperature of 78F: Built in electronic thermostat, Model No. PH100 would automatic heating water then maintain the temperature at 782 which is an ideal temperature for most of tropical fish. No adjustment needed, so not adjustable, please kindly note before order. Shut off Automatically: LED indicator light would display red while its turned on