Reef Keeper- Outlet kill?

I would think in the sump would work better for what you are trying to do. Running it in the sump would also shut it off when the water level gets too low from evaporation also. Running it in the display wont shut it off in that scenario. For that reason, I would say the sump is a better place for it. Then its doing double duty.

 

I'll play around with this. I will also want to put this on a timer as the water will reverse-siphon back into the sump after the pump is trigged to stop by the water dropping in the sump. The returning water will cause the float to switch the pump back on as the water rises in the sump.

 

Set the "ON" high enough that full water won't trigger it. If its only purpose is to control the pump due to wave motion it wont be an issue. Just don't use that particular float for ATO uses.