The only problem I see in using 1 high wattage heater, is if it gets stuck in the on position, it can cook your fish (this has happened to me), I now use 2 smaller heaters in each sump, if 1 fails in the stuck "on" position, it may raise the temp, but not to lethal levels, and more than likely, the other heater will turn off.
F1Vets suggestion of a temp controller is the best practice of all.
F1Vets suggestion of a temp controller is the best practice of all.
