I recently set up a 20 gallon reef tank and this is the fourth heater I have tried, and I should have just spent the money on this to begin with instead of waste time with $13-20 heaters. I have Reef-Pi set up monitoring my water temperature, and also have all of my equipment plugged into a smart power strip which reports power usage. So over time I am logging the exact temperature of my water, along with how much power my heater is using. Pretty much every heater out there operates in a fashion where it turns on full power to heat up the water, then totally turns off until the temperature drops and it needs to heat again. This AquaEl heater is way smarter though. When I initially put it in my tank and set the temperature, the heater would raise its power by around 8W every couple of minutes until it hit its max draw of 76W. Here's the smart part though: Once the water got to the set temperature, the heater dropped its power to around 34-37W and stays there all the time. So instead of cycling on and off, it sets itself to the correct temperature needed to maintain the water. Looking at my temperature graphs over the past 12 hours, the water has fluctuated +/- 0.1 degree. This is truly as steady as you could hope from an aquarium heater. All heaters should operate this way. The build quality of this heater is outstanding as well, and obviously the compact size is great for smaller AIO tanks like mine. I will admit that the instructions for setting the temperature are a little confusing, and I'm still not entirely sure if I have it set to 76 or 78 degrees, but my water is right at 76.5 and steady, so that's fine with me. Seriously, buy one of these.