ATO, Stop siphoning?
 

I am building a ATO for my tank. Have a 24V control board built witrh relays to operate the pump. But, when the ATO level is higher than the sump, how do you stop siphoning? I guess a Peristalic pump is the only option? Have been told that people use a powerhead, like maxijet mp1200. But that would allow siphoning, won't it?

Have the top-off go into the display tank rather than the sump.

Ohh, ya, DUH, that will work great. Thx. Ordering maxijet now

Can you just use a float valve and scrap the pump? Gravity can be you friend in this case.

No, not really. ATO tank will be at sump height, for bottom, but ATO tank is taller, so, gravety only work for half a tank. Want more volume

Don't submerge the output end of the ATO pump.

I have the surface of the ATO jug lower than the outlet which is above my sump (not in the water). When the pump shuts off the line drains back to the ATO jug.

As untamed said don't submerge the output to the sump and put a siphon break hole in the output line just above the water line in your ATO reservoir.

this is what i have done, my res is higher than my display and i top up in the sump. never had a problem.

could you use a NC Solonoid valve