I could probably chat about sumps with you all day lol. I love em.The downside of a sump for me, is if you have minimal to no water movement inside the tank, i.e. your return is just in one place; in my experience with a spray bar that runs the full length of the aquarium and a pump rated for 1920 GPH, with 4 ft. of head pressure = 1600 GPH, and a tank turnover rate of 6.27x per hour, i get sitting fish waste. I am now running an Eheim 2217 subfilter + canister filter in order to alleviate the siphoning of fish waste. Subfilter is filled with mechanical media, while the can is filled with another 4L of pond matrix. I am thinking of getting a wave maker right now to just push the waste to the other side of the tank, in addition to getting another 2217 subfilter + 2217 can, which I would put on the same side of the tank that the current setup is running on, and where I plan to point the wavemaker to push the waste to. I could probably go 3 months without a WC or canister cleaning, and my nitrates won't go higher than 100 ppm; but that's just bad fishkeeping, besides the fact that WC help regulate growth inhibiting hormones of bichirs.
Please keep us updated on your final build that you would execute.
HFK.
The returns arent necessarily restricted to once place. You can make your own spray bar or by using loc lines you can basically aim the returns any where in the tank. I actually think theres greater oxygenation with sumps depending on the design. Decent sized overflows would create allot of surface agitation. Plus you can always throw a bunch of airstones in the sump