I'll be using my Apex to control the temperature as well. I mostly went with this heater because it is much shorter than my JBJ titanium and it will fit in my sump.
So did you just order the heater or with the controlor as well?
I ordered both with the idea of having my Neptune turning on the Finnex controllor. Looks like a may have wasted some money Well at least I have a spare than, i'm a bit of an equipment hoarder