The heater should be immersed into water completely. It takes about 10~15 minutes to get used to the water temperature. Then adjust and set the desired temperature value. It starts to work if the actural tempeature value is lower than the setted value, unless it doesn't work.
Features:
* High quality: Aquarium heater made of high quality stainless steel tube. Antiflaming heater cover can prevent fish from going too close to the heater.
* The heating rod is explosion-proof , shatterproof and waterproof, anti-rust, useful and durable.
* Suitable for fresh water, seawater Aquariums.
* High efficiency heating module.
* Sensitive and reliable thermostat: Control Precise Temperature levels?Adjustable temperature, use intelligent temperature chip control circuit, with external temperature adjustment function. The temperature range in this accurate thermostat is 20-34 ?(68 -94?).
* Automatic shut off when the temperature is reached.
* Double sensing probes on the top of heater provide more precise induction.
* ON/OFF switch and Adjustable temperature controller.
* Antiflaming heater cover can prevent fish from going too close to the heater  
* Easy to use and install : Heater is fully submersible and can be placed horizontally or vertically in your tank. The aquarium heater thermostat has three suction cups,to make it easy to attach to fish tank, heating leaves and fish separated, so that fish keep safety.
* There is indicator light to show the heating status on the LED screen through the temperature control.
* You can long-press the 'Set' key to shift degree unit between Celsius and Fahrenheit
* Suitable for Fish Tank 250-350L-voltage 110V, power 500W, heater rod length 10.2inch/26cm. The controller power cord length 5.5ft/170cm
 
Specification:

• Materials:Stainless steel
• Color:Silver
• Power:500W
• Voltage:110V
• Fits Fish tank size:100-120cm
• Suits for Water Volume:250-350L
• Heater length:26cm diameter:23mm
• Power cord length:1.7m
• Temperature control range:68?-94?/20-34?
• Waterproof level:IP68  

Package Include:

• 1 x 500W Heater(with power cord & plug)
• 1 x User manual
• 2 x Suction cups