Ideas to improve custom sump design?

[Trigger88]

Background
Hi. After decades of freshwater aquariums we just made the leap to salt water with the purchase of a previously owned 48x24x24 Display Tank currently hosting Fish Only With Live Rock (about 100 gallons of water). Some day in the future we may add some soft corals but nothing more extravagant. The sump that came with the setup does not have room for a refugium and we would like to add one. After researching various options on how to do this, we have settled on a single larger sump due to the safety it provides if pumps or check valves or ATO fails. I mention all this to let you know our intent, and if you have any better ideas, please let us know. We are looking for suggestions!

Sump Design
I am looking for a 35”L x 18”W x 17” H sump. It’s the biggest length/width that will fit in cabinet. The height is sized to allow an ATO tank to be lifted over top vertically without tilting it in order to install it next to the sump. Attached is a graphic depicting the sump design.

The Overall Layout is designed around a square section for Refugium to maximize equal light (approximately 18x18 holding 13 gallons, about 13% of display tank size, which is within 10-20% size for Trident Method should we ever decide to try that out). Planning to use a Kessil H160 for light (18"x18" area). Having the refugium on the end also seems like it will be easier to shade the other sump areas from the refugium light.

Section 1 is sized to “just fit” a 7” Klir Roller Filter with filter bracket. I also want to make sure a 7” filter sock would still fit should we ever need to revert to that. The water will flow under the 16.5” high wall to Section 2.

Section 2 is designed for the skimmer and heater. It is slightly over-sized for future expandability. The water will flow over the 12” wall to Section 3.

Sections 3 & 4 are the refugium. I struggled a little with how to design this section. I initially had it as one big open area but was concerned that the water flow would allow for dead spots in the corners. The current design breaks the refugium into 2 sections (Sections 3 & 4 on graphic). I did this for a few reasons: (1) it potentially provides a better sump structurally with a single piece of acrylic running down the entire length of the sump; (2) it provides flexibility/options for the future; (3) hopefully makes water flow through the entire refugium with no dead spots; and (4) not sure if this is a real reason or not, but seems easier to grow multiple species of macro algae for biodiversity. I also struggled with how to get the water from Section 3 to Section 4. A perforated wall? Underflow? Overflow? I’m thinking that a perforated wall will provide the best flow through the refugium? The idea is that all sections shown in green in the graphic would have a water level of 11” but the top of the teeth would be at 12” height or so.

Section 5 is the Baffle or micro bubble trap. I’m not sure if we will actually see any micro bubbles travel that far through the fuge, but just in case we change something in the future, I thought it would be prudent to have a trap here. I have seen many designs for this online with 2 and 3 wall designs, “over” first, and “under” first. I’m assuming they all work since all designs are seen in abundance. I decided on a 2-wall design vs. 3-wall to maximize space for other stuff. I chose an “over --> under” approach in hopes to best keep the macro algae in the fuge area. Also, how close can/should the 2 walls be? I guessed at 2 inches to allow for cleaning in between. Let us know if you have a better idea.

Section 6 is bigger than my current pump but has room for expandability should we need a larger one.
Questions
1. Sump is designed for ¼“ thick acrylic. Is that thick enough?
2. Recognizing that the refugium light (Kessil H160) will be sitting 8-12” above the 11” water height in the refugium, light may spill over into other areas. Any ideas on how to minimise light leakage to the rest of the sump?
3. Where would be a good place to put a bag of activated carbon?
4. How close can you put a return pump intake to a wall?
5. Any other ideas on how to make the sump better or more user friendly?

Thanks for reading and thanks for any ideas you may have!

[Sk8r]

Mine, pro-built, has 2" for downflow, with a transverse slit 2" below spill line, to let water equalize on either side of barrier. Then about 15" for central compartment, holding skimmer, heater. and about 10 of those inches occupied by a rock rubble pile (spare bits for use if needed for, say, coral base.) Then a 1.5" gap, with a .5" gap at bottom of leading wall, then no-gap under the final wall. This prevents fish that may get into sump from reaching return pump. Flow is an under-over to the final chamber, about 8" for return pump. h