I have been designing a new custom tank with sump, and would appreciate any feedback on the dimensions and drill plan, especially regarding flow. It will be a peninsula layout, although not visible from behind. I would like to have no equipment other than the overflow box and return visible in the tank. Pictures first:
You can also view and download my current 3D model.
The main geometric constraint for this tank is depth. The main walkway through the house is directly in front of the tank, and there's other furniture about six feet away from the wall. The standard two-foot tank depth is definitely too deep; I think I can get away with a 22" deep tank, but it has to be almost flush to the wall. The current tank dimensions are 5 feet long, 22 inches deep, and 24 inches high.
Because the tank is visible from the front and right sides, because I'm tight for depth, and because I want to minimize equipment visibility, I'm planning to place both the overflow and the return on the left side of the tank, with the overflow in back and a single 1" return line drilled in front of it just below the water surface. (Hence "peninsula"; although it's only viewable from two sides, the back is not available for plumbing.) This would, I hope, act a little bit like a traditional canister flow pattern, with the water traveling across the front of the aquarium and then returning at lower velocity through the rest of the aquarium volume.
I'm not married to that layout, but I'd really like to avoid using circulation pumps or having any plumbing on the right side of the tank (tip of the peninsula). I have considered running a closed loop through the bottom of the tank, or using clever siphon breaking techniques to allow sump returns at the bottom of the tank, but I think either option introduces excessive complexity. I'm also planning automatic dosing and water changes; I really would like this build to be as straightforward as possible.
The sump will be a 40b with sock filters and some sponges. The CO2 reactor, UV sterilizer, and any other accessories will be on a separate circuit running to and from the sump. The overflow is currently a Synergy Reef 16" Shadow; it's a little bigger than I need, but I want three drains. I've currently planning to run the return line straight into a 1" bulkhead, with no nozzle to speak of. I will probably fit a stainless steel mesh over the return to prevent anybody climbing in when the pump's off. I also have the capability to 3D print custom nozzles/diffusers. I could also have the return come over the rim, but all the solutions for that I've seen are a bit unsightly, especially since the return will be in a highly visible location. The downside of the no-nozzle bulkhead design is that there's no siphon loop; the tank will drain to the bottom of the bulkhead, rather than just until the nozzle starts gulping air. A two-inch drop will put something like twelve gallons into the sump, which is definitely doable but would require me to keep something like a third of the usable volume of the sump empty.
The return pump will likely be a DC variable-speed pump, either a Jebao or something that I can control with a 0-10V input. For now, let's say that I'll be able to set the overflow/return flow rate to whatever I want.
I generally expect to have some significant hardscape and heavy planting, but with an islands or sloping layout that leaves plenty of open space in the top front and top right (peninsula tip) of the aquarium. I may want to have some emergent growth, which would likely complicate flow patterns.
Fauna hasn't been chosen. My main "bad idea" is to have some rainbowfish mixed in. I say "bad idea" because I really don't want to put a cover or canopy on the tank, and I know they're occasional jumpers. Also, I may end up needing to run the return flow at relatively high velocity, which I understand some 'bows don't like. I currently have the waterline set two inches below the rim in a bid to make it a little harder to jump out. There seem to be different opinions on where to put the waterline in a sumped rimless tank anyway.
This project isn't budget-constrained, within reason; my priorities are (1) reliability, (2) simplicity, and (3) cost. I'm tentatively planning to order the tank and stand from "Custom Aquariums." I'm not a big fan of their black silicone, but otherwise they seem like a good builder.
I plan to post a full tank journal at some point; I also have an interesting but conservative design for an automated water change/dosing system that I'd like to run by the community. For now, I'd really appreciate anyone's thoughts on whether this design is viable, and especially any input on how to choose the dimensions and drill locations!
Here is another link to the 3D model, which is viewable online and downloadable.