If you're going to automate then you may as well automate as much as possible.
I monitor the following through Hydros:
- Temperature
- Leaks
- Sump water level
- pH
- Main tests - NO3, PO4, Mg, Ca. I have manual tests if an automated test comes back out of range.
- Alkalinity
- Skimmate collection fluid level
- Salinity
I automate the following:
- Heaters. While most good ones have their own controllers, having them controlled by your controller is a necessary backup.
- Return pump control, with dependency on leak sensors.
- ATO with dependency on sump water level.
- Alkalinity dosing, with dependency on Alk testing.
- Kalk reactor pump and stirrer.
- Dosing trace elements.
- Lights for scrubber (or refugium if you're using that, instead).
- 4 wavemakers with varying schedules.
- Carbon reactor (though that's not up and running right now).
- GFO with dependency on PO4 test.
- Biopellets with dependency on NO3 test.
- Ca and Mg dosing, dependencies on their respective tests.
- NoPox dosing, because I let my NO3 get out of control.
Currently I'm using a Mastertronic for the NO3, PO4, Mg, and Ca testing, but will be switching to the Maven once it's released. I had been using the Dosetronic for dosing, but it nuked my tank twice and I now chalk that up to a waste of money.
The only thing I have to do manually is adjust the salinity (if necessary) and feed. I don't want to automate the feeding for two reasons: 1. It forces monitoring of the tank every day and 2. I create my own frozen food (which led to my NO3 problem but that's another story).
Of course, maintenance is a manual task, as well. Cleaning the skimmer, cleaning the scrubber. Things like that. Plus pump maintenance.
I don't do water changes, but may in the future. That's another thing I can control through the controller, turning off various devices like the ATO during the AWC process.