Just one 200 watt heater will be more than enough. Check amazon, you wont need more than one at all. That's a small tank, if you really want more get the 250 and you will be able to use it for anything up to 100 gallons.
Aqueon Pro 200 Submersible Aquarium Heater lifetime warranty, shatter proof, light showing they are on and different light showing when heating, great heater.
125 Gallon Cichlid tank
NEW PEACOCK BASS !!!!