The Red Sea doser I’m pretty sure has no integration with apex would need to use the red sea app. Only thing that comes to mine potentially if you wanted to use Apex would be setting the doser in the red sea app to continuous, if even possible and then controlling the power power to it via the Apex. However even if that works you’re probably only gonna be able to use one of the two heads
You would set the out let to auto and apply a code in the advance option something on the line of.
Fallback off
Set off
If phprobe < [your desired low value to turn on] then on
If phprobe > [your desired max value to turn off] then off