Water quality testing

So I had the idea of having a water quality monitoring/testing system, that is totally electronic, (no test strips, etc), that I can hook into a computer and monitor on a constant basis. I would be looking to use the system in tanks between 50 - 300 gallons. I haven't seen anything on here about this so I was wondering if anyone has any recommendations about a system like this, past experiences, possible equipment, etc.

Thanks