I used this heater for about 2 years with a 50 gallon reef tank. After 2 years it developed an internal leak which shorted out the heating coils and tripped my ground fault circuits. In addition to shorting the coils a small amount of water was leaking from the temperature adjustment knob. Because this is the only in-line heater I have found I purchased a second unit to replace the first one. After 2 months it also developed an internal leak and shorted the heating coils. I am now using an in-tank heater.If anyone knows of a good inline heater to use instead of this one please let me know.