This is the setup i'm using in my garden pond and have been refining over a number of years. If you are like me and do too many things at the same time i'm sure you have forgotten the tap water on a number of times leading to overfull pond and waste. This is the number one reason you need a Pond Control if You own a pond. Then of course if you have problems with alges or suspect bad water quality then you want to know that too, right? In this setup I have a number of sensors from Atlas Scientifc (PH, ORP, EC, DO and temp). The water level is controlled by water solenoids, also measuring the fill flow and level with Milone etape or other liquid level switches. Everything is monitored and controlled by a number of services (docker containers) using the TICK stack, accompanied by a web server, all running on a RPI4. You get control and can create nice dashboards with long term trends. The project includes models for boxes and sensor mounting as well as schematics.