Here's what the Secondary and Water Change tanks look like.
The plumbing connecting the Water Change tank to the Secondary Sump that you see there has actually changed. I had to drill a third 1" hole to support the flow and so it now looks like this actually.
Basically, water drains out of the 131g display into the Water Change sump. As that tank fills/overflows it flows into the Secondary sump. The emergency overflow is plumbed directly to the Secondary Sump. The Secondary Sump is connected to the Primary Sump with a 1 1/2" line.
Water is drawn through and out of the sumps via the return section of the Primary Sump which house two MagDrive pumps. Here's the line (3/4") going to the 131g.
One of the reasons for this whole exercise is to finally realize my dream of automatic water changes. Here's how it will go down.
1. Feed to the 131g tank is cut (via the controller).
2. Two float switches and one pump will reside in the water change tank. Water is pumped out of this tank until the lower float switch is activated. This pump is plumbed to a drain in the basement. (I cut a hole in the floor to support this).
3. Once the first (lower) float switch is activited that pump-out pump is shut down and the pump-in pump is triggered which pumps in newly mixed salt water from the basement reservoir. This salt water is pumped in until a second float switch at the top of the water change tank is triggered.
4. Once the water change tank is refilled the return pump to the 131g tank is turned back on which pushes the new water through the system.
Still missing a few parts to finish this bit up so stay tuned for a demo once it is all in place.