The Tetra Submersible Heater will display a red light when it is currently heating the water in your fish tank. If the device isn’t showing this color, then you can take a look at this troubleshooting article at Aquarium Blueprints to see what you can do.
Before we start, it should be noted that this guide is based on the 50-Watt, 100-Watt, 150-Watt and 200-Watt versions of the Tetra Submersible Heaters, including the HT10, HT30 and HT40 brands.
1. For the first step, you can test the temperature of your fish tank by using a thermometer.
If the temperature is somewhere between the range of 76°F to 80°F (or 24.5°C to 26.5°C), then it may indicate that the heater is currently working. As a result, you shouldn’t see a red light coming from the device it won’t turn on unless the water temperature falls below 76°F (or 24.5°C).
2. Another potential fix that you can try is to reset the Tetra Submersible Heater by doing the following:
- Unplug the heater from the power outlet.
- Let it sit in the tank water for at least 15 minutes.
- After a minimum of 15 minutes have passed, take the heater out of the tank.
- Let the heater sit in the air at room temperature for at least 15 minutes. If the device is covered with algae or other grime, then you might want to clean it off before letting it sit in the air.
- Once at least 15 minutes have passed, put the heater back into the tank water.
- Next, you should wait for another 15 minutes so that the device will get re-adjusted to the water temperature.
- Once you are done waiting, plug the heater back into the power outlet.
3. Another step you can take is to re-position the Tetra Submersible Heater. This product works best in areas with a high flow rate, such as a filter intake or air stone.
We also recommend placing it diagonally or horizontally to help with provide more efficient heat dissipation and accurate temperature readings. You should also place it as close to the bottom of the tank as possible.
4. There is a possibility that only the light of the device is malfunctioning while the other components are working correctly.
To see if this may be the issue, try to observe the heater to see if you see any heat wave and/or bubbles. This could indicate that the device is still heating your tank water.
Of course, you should also test the water temperature at different times during the day to see if the it remains above 76°F (or 24.5°C).
5. If you see no red light and the heater does not appear to be raising the temperature in your aquarium, then the device may be defective.
In this case, you will need to replace the Tetra Submersible Heater. If your product is still under warranty, then you can try contacting Tetra about getting a new replacement.
