Most of these heaters require the pump be on before, or at the same time, as the heater. Some even say to purposely put the heater on the same switch/breaker as the pump. What I've always done is to use a timer and put the pump together with the heater on the load side of the timer.
Also, some heaters require what is called a "fireman's switch". This would turn the heater off 15 minutes before the pump goes off. This is so the heater has time to cool off before the pump stops. The "fireman's switch" is just a micro switch that mounts on the timer wheel (usually Intermatic brand) and trips 15 mins before the off tripping lever for the whole timer. The switch has leads that you run to their control board and shuts off the heater.
You may not have that type heater and only require that the pump be on. If that's the case just make sure the heater comes on with the pump. So in answer to your question, yes you can put the heater on with the pump as long as they are not pulling more than your circuit size.
Of course the timer or switch is fed from a GFCI breaker.
