Review on BoxTech Aquarium Heater - 50W/100W/300W Submersible Thermostat with Adjustable Knob, 2 Suction Cups - Suitable for Freshwater and Marine Saltwater Environments - Explosion-Proof by Ashley Turner

I kept it in a 5 gallon tank for about a month. So far it keeps my tank at 79 consistently, but it took a bit of calibration to get it right. As with any heater, don't rely on the dial to get the temperature you want. Get a real thermometer and make taking your temperature part of your daily routine. I'm giving 4 stars because the cord from the dial to the plug is ridiculously short. Luckily I don't have to adjust it often, but I would prefer a longer one. This heater is inexpensive yet reliable. If I live a few years I consider it a good buy.