I just got a JW Fusion Smart Temp Aquarium Thermometer and a Eheim jager trutemp submersible heater 75w for my 20 gallon high tank. Have heater on 76. Thermometer has shown 81 since I put it in and that was before I plugged heater in. Thermometer works fine outside the tank. I put it on my fridge and the temp dropped like it should. Been stuck on 81 all day and just checked it this morning It still shows 81. Is the thermometer not working right?? What do I do?
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