Review on hygger 50W Mini Submersible Digital Display Aquarium Heater: Compact, Fast Heating & Thermoregulation for 🐠 Small Fish Tanks, with External Controller & Built-in Thermometer - Ideal for Betta and Turtle Tanks by Leslie Aragon

I bought this heater for my hospital aquarium because it has adjustable temperature control and I sometimes need a higher or lower water temperature depending on what fish need to be quarantined. After weeks of trying to get this to work, I'm sending it back. The instructions say it can change a degree, but even if left at the same set temperature for several days, not only will it change 3+ degrees, it won't maintain a constant temperature at all. It's 76 one time, 74 in a few hours and maybe 78 with a bit of luck. I also didn't want to risk it getting too high and killing my fish like other reviewers have done. What's the point of having an adjustable temperature if it doesn't maintain an accurate temperature?