Nice looking tank, Lori! Definitely agree looping in some alk mg ca testing for the corals and looking at protein skimmers. I've had several HoB(Hang on Back) skimmers that were great, and others not so much. If you're having success with the canister filters, I'd keep running them while researching, and posting questions about sumps. Planning out a sump (How the water flows through it, where all the equipment goes, and how everything is going to be plumbed together) is one of my favorite parts of the hobby. Refugium planning is equally awesome! Macro algae, micro fauna, and rubble - Oh my! Nerd out on it and devise your setup just the way you want it.
Noteworthy mentions if a sump interests y'all based on your original postings!
1. There are few of easy ways to keep your sump from overflowing in the event of a power outage:
-Drill a hole in the return line to cause a break in the siphon and stop the flow of water where you want
-Use a check valve
-UPS (Uninterrupted Power Supply). These are batteries/surge protectors that keep your critical pumps going in a power outage.
2. If drilling a tank for a sump is intimidating don't worry about it. There are overflow boxes that do an exceptional job out there! I've been using them my whole journey through the hobby. They require a peak at least every so often to make sure they're operating at optimal capacity, but whats a quick peak when you're going to be checking out all the cool things going on in your tank anyway?