Review on 🐠 Hygger 500W 800W Submersible Fish Tank Water Heater with LED Digital Temperature Controller - Ideal for Saltwater and Freshwater Aquariums, Fast Heating for 60~180 Gallon Tanks by Azeem Mendez

I'll start with the good. Warms well and keeps the temperature stable. The tank (75 gallons) is in a heated room (about 70) but near the outside wall of my basement in upstate New York (cold!). I had 2 300 watt heaters that just couldn't keep the temp in the tank above 76.5. I took out one of the 300s and replaced it with the 800 watts shown and now the tank is hovering between 79.1 and 79.5. But the sensor is off. I have a separate single sensor digital thermometer as well as a glass thermometer (as well as a point and shoot thermometer) so I'm sure of the actual temperature. The gauge on the heater is set to 83 and shows 82.2 and the actual water temp is 79.4 (reading it as I type this). Not too much of a problem since I know what temperature is, but it would be nice to have an accurate sensor or even the ability to calibrate. That's the ONLY reason I took off a star. Otherwise it does what I was hoping for. Install it and forget about that heater in the New York State winter. Please note that this is not a permanent heater. A little on and off. It took about 2 days to increase the temperature from 76.5 to 79.5. I believe this is done so as not to stress the fish. In general, I am happy with the heater. If they had done it with calibration it would have been a 5 star heater.