The heater that I had went psycho, it didnt start heating untill 70 and then sometimes wouldnt shut off untill 90. I had to get a heater quickly because my fish were comming soon. I just went to walmart (before i started this thread) and bought a cheep submersible Tetra heater. It was supposed to keep the temp between 76 and 80, and it didnt even raise the temp past 75-76. I complained to tetra and they sent me an additional heater. I personally like the heaters you can set yourself, but these tetra heaters dont let the water temp vary more than a degree, so if thats the temp you want then they work great. Like I said when i buy another heater it will be a visi-therm stealth pro.