Review on 100W/300W/500W/800W Submersible Aquarium Heater with Intelligent Temperature Probe and LED Display External Temperature Controller for Fish Tank 5-158 Gallons by Nancy Russell

Instead of an aquarium, I used 20 gallon semi-thaw drums in which hardy water lilies and water lotus bulbs overwinter. After the temperature dropped to zero and below zero, a few inches of ice formed on the surface of the water, even in the garage where the half barrels are stored. If the ice reaches my plants/bulbs, they will die. After breaking the ice, I was able to attach these heaters to a plastic liner in each half of the keg, set the thermostat to 68 F (the lowest setting), and melted all the ice in a matter of hours. (In the photo there hasn't been a heater in the upper bin for a very long time, so there is still a lot of ice.) After that I turned the heaters off again. They are very easy to set up and use! Good product!