Instructions
Unplug the heater and plug it into another outlet while watching the red indicator light that shows the heater has power. The issue could be something as simple as a bad power outlet or a failed power strip.
Unplug the heater and wait at least 5 to 10 minutes to give it time to cool down. Remove the heater from the tank and examine it closely.
Remove any visible corrosion from the outside of the heater using a solution of vinegar and water. Minerals from hard water can build up on aquarium equipment, including saltwater heaters and filters. Those minerals can cause corrosion on the heater and interfere with its normal operation.
Turn the thermostat knob to a higher setting before putting the heater back in the tank after cleaning. Setting the thermostat to a higher level will make it easier to see if the unit is working, since you can simply watch for the temperature in the tank to increase.
Place the heater back in the tank and plug it in. Watch the thermometer on the tank to see if the temperature goes up after a few minutes. If so, the heater is working and you can turn the heater thermostat back down to the desired setting. If not, the heater is still broken and you should replace it with another as soon as possible.
How to Troubleshoot Saltwater Aquarium Heaters
No matter what kinds of fish inhabit your saltwater aquarium, the heater is one of your key pieces of equipment. Saltwater fish need a consistent temperature to stay healthy and active. If the temperature rises or falls too much, those fish become susceptible to disease and other issues. Use a quality thermometer to monitor the temperature in your aquarium, and check any suspected problems with your heater immediately.