Heater Size

[sphelps]

I run a single 300W on my 100gal + sump.

If you go with two smaller heaters you should run them on a single controller so they both turn on at the same time, otherwise syncing them will be difficult. If they are not synced only one will be primarily active and if the wattage is too low the duty cycle will be longer which could cause premature failure and less stable temperatures overnight. For this reason if you wish to use two heaters independently be sure to use two larger models, I would suggest two 300W units over 200W units unless a controller is used. Or use a primary unit at 300W and a smaller unit for backup.