syphon

I have Red Sea ATO+ and I want to put my ATO container on top of my sump but I am not sure if the flow will stop when the pump stops or it will create a syphon? And another question is it safe to put it on top of the sump in terms of weight will the sump be OK. THe container is about 20l. Is...

Hey everyone, Need some help with getting my full syphon tuned to get the system quite. The tank was already drilled when I bought it. Not sure what I'm doing wrong Will attach pictures and will greatly appreciate any advice! Thanks