Maybe this is a late reply,but
I have 4 tanks plumbed into a common sump 75, 75, 40 and 20. I ran tubing to all from a manifold, going through a single return pump and uv. Had to install control valves for flow. Pvc drain to the sump that can be channeled through a filter roller or bypassed with valve controls. I did dual returns in case of backup in one line.
1 skimmer, 1 apex controller with triton, gfo/charcoal reactors and dosers for all 4 tanks in one 16x 40 sump. No problems over flowing, I cut power for pictures in the frag tank regularly. I love it. Looking at adding another 1-2 tanks to this system. You tune your working water level to accommodate for when you cut power, as long as sump is big enough. Also water changes are easy, I have a pump in the sump that pumps to a drain and a pump at mixing station that pumps into the sump.