I'd recommend you go to 2 X 100 W heaters instead. There's a huge misconception that discus cannot handle cold water. They can't handle rapid changes, but a gradual drop of 15F when a heater dies poses no problem. Day/night temperatures in the Amazon vary by more than 10F. But running two huge heaters can result in your cooking 24 discus. I've lost entire tanks of discus when a heater gets stuck. It's not fun at all.