Sump water level

[JohnJoseph]

Is it better to keep sump water level at marked "highest" and manually add RO or keep water level at "lowest" and let ATO do it for you? Which is better for parameters?

 

[EeyoreIsMySpiritAnimal]

Is it better to keep sump water level at marked "highest" and manually add RO or keep water level at "lowest" and let ATO do it for you? Which is better for parameters?

Keep it wherever your skimmer is happy

 

[EeyoreIsMySpiritAnimal]

Is it better to keep sump water level at marked "highest" and manually add RO or keep water level at "lowest" and let ATO do it for you? Which is better for parameters?

Why couldn't you use an ATO regardless?

 

[EeyoreIsMySpiritAnimal]

You need to consider how much of your tank will drain into the sump when the pump is off too.. I also made sure my (internal) overflow box can drain into the sump without it overflowing...

 

[RocketEngineer]

I set my water level to be about 1-2 inches below the rim of the sump when everything is off. I use the return pumps to fill the display initially. Once the display starts overflowing, I turn off the returns, top off the sump to the 1-2 inch point, then start it all up and let it stabilize. If all is well, I mark that level in my return chamber of my sump, mark the off condition level, and now I know returns on or off what my level should be.