Review on 🐠 PERSUPER Aquarium Heater 100W/200W: Submersible Fish Tank Heater with Adjustable Thermostat 68 to 94°F, LED Display - Fast Heating Water Temperature Controller for 10-40 Gallons by Victoria Brown

I bought 4 of these for 4 10 gallon tanks. None of the 4 works properly. I tried to test the temperature from 74 to 92 degrees. Every time I adjust the temperature setting, they heat up for a few minutes, indicating the water has reached setpoint, but in fact it has never exceeded 74 degrees, the room temperature is 73. It seems there is one now Problem with the flow through the heater, but I've tried changing the position several times to no avail. I'm glad I tested them before putting the tender fry in aquariums.