@endy0430 if you’re letting the ink bird do the actual temp control then your Apex becomes more of a fail safe if something goes wrong. Same basic idea as if the Apex was running your heater but with parameters wider than the inkbird. I think the Apex has a macro to set up the heater. But here’s some basic code. I know others will have lines to add but this is a start.
ALSO, there is a great Apex programming guide in the Aquarium Controllers Forum
Fallback ON
Set ON
If Temp > 81.0 Then OFF
If Temp < 70 Then OFF
FWIW the Temp < 70 is in there in case the probe goes bad or falls out of the sump.