This is a great thread because this is something I need too. I want it for an ATO system so that my skimmer works at its prime. I've been losing 1-3 gallons a day. I don't know why the fluxuation. My question:
Would a 5 gallon dosing container work if you didn't unscrew the back
that lets the air in ? Then all you do is make sure the line is at the point in your sump that you want the water level ? Do auto top off pumps syphon water in if the power goes out ? Whats better ?