Since I currently don't have a sump, I have been just siphoning from the tank, then dumping into the top. My new tank will have a canopy, so I would like to do the water changes through the sump. I'm not sure how to go about it, though. The sump will have an inlet/filter sock section (small-ish), skimmer section, refugium section, and return section. Where do I pull the water from? Can I install a valve to close the return going back to the tank, open one going to a drain, and use the return pump to remove water? How do I know how much water I removed? It seems like the water height in the sump is going to be determined by the height needed in the skimmer chamber, but is there some way to just fill back up to a certain point? I've never had a sump, so maybe it's more simple than I'm making it out to be. I want to plan with plumbing if I need to, though.