Okay, so I have a 16 gallon with a filter and a heater. I got a 100 watt heater from Petco (their brand) and it's awful. It doesn't have a temp indicator so I'm working on guesswork. I want to replace it and I'm looking for a decent submersible that you guys have had good experience with. Also, I'm thinking of going down to 50 watts. This heater is always running higher then it should. Right now I have it at 78 but it will probably creep up to 80 by morning. It's driving me bonkers. Any suggestions on a good heater?