Good point DMorty. For clarification, my sump is completely empty just water. I am planning to put some live rock in one of the sections but definitely no snails and no kalk dosing so no issue there. If I make my own ATO using my own design I am confident that it will be of good quality. The only weak link would be the float switches. ATO are simple designs with a relay so as long as I can get a good quality float I think I should be okay.
So what I need is some encouragement for me to get my butt up and do it.