I build my own scrubbers, & have a 220 litre system, so tiny compared to your swimming pool full of fat fish
Thinking aloud; on a tank the size of yours with heaps of fish & feeding, 2 things I would do are, have at least one big skimmer to remove as much particulate matter/detritus as possible, & have very efficient mechanical filtration to do the same thing. Plus, have really strong flow in the display to keep the detritus suspended so the corals can get as much as they need, with the rest going to the sump(s) / filters.
In regards to a scrubber, they are a great weapon against inorganic nutrient build-up, which is a consequence if heavily feeding a large amount of fish. The typical way of determining the size of scrubber needed, or specifically the screen size needed, is to determine the amount of food being fed to the system on a daily basis – measured in cube equivalents. Then using that number in the calculation. On a system as large as yours a massive scrubber is not the answer, but perhaps multiple units.