+1 Rancos are solid, and a dedicated temp controller is a must in this hobby. An aquarium controller is a better way to go, but if money is tight, a temp controller is a good alternative. The system I use, which is basically bulletproof is this for my 125 gallon.
200 watt heater in the tank. Internal thermostat set 1 degree above tank temp. On/off controlled by my apex. Set to latch on in the event my apex fails.
200 W heater in my sump. Set 2 degrees above tank temp. On/off controlled by my apex. Set to turn off if my return pump is off, my high high float triggers, or my low low float triggers. Set to latch off if my apex fails.