randomly stumbled upon this because I am trying to generate a 0-10v apex like control from my system to manage the speed of my pumps. I am slowly getting rid of ecotech stuff because it is so closed. So a new pump on the way takes apex style 0-10v. Anyway...
Here is my setup...in case it helps anyone who wants to DIY it. I'll get around to putting the code and detail on GitHub.
It measures the main parameters, watches the sump level, pump details and other instrumentations so I can start and stop things as needed.
For example, I have a process on the RPi in Node-red that turn on and off the heaters. But I have a second process on the Ubuntu system that watches this information as a backup process. All of these are on UPS. I recognize this is a bit extreme

but...don't judge! HAHAHA!
My favorite part is how I can control everything in HomeKit, so when I go to the basement to check on something I can turn things on and off on my phone.
Also, since this is mostly mediated by MQTT I can create synthetic devices. For example, I have a device called "do swap" and that turns off the pump, stops the heaters, and a bunch of other things and then turns on an evacuation pump for 15 min. Then turns on a pump to put saltwater back into the sump. But it only does this if the swap salt is close to the same SG/pH/Temp as the tank.
Once you instrument...you can do lots of stuff!
If anyone is interested I can detail out the sensors and wiring and other things.
My goal is to make this easier on the next person! So ask away...