jjohnwm
This is what my current universal design looks like (dont judge my ms-paint skills). The water enters on the right and keps a more or less horizontal flow throughout. There is no strong sucktion on the right keeping smaller fish and shrimp save.
In my tank lots of snails and amphipods live in the coarse sponge breaking bigger peaces down and keeping the bacterial coat from growing to big. I have yet to clean the coarse sponge, it all (as tiny poop pellets) just ends up in the fine one which I clean frequently. I think this is a good way to remove the waste as it does not built up to much and starts being broken down to a molecular level. It also leaves the biological filtration intact, so the cleaning has a minimal impact on the water quality.
The choke point is the fine sponge, the fuller it gets the less water cycles, so try to give it as much surface as possible and clean it regularly. I made a bunch of them so people sitting my tank just need to replace them.
