My 75 grow out (won’t have all of these fish in it at the same time) is getting equipt with a 40 breeder sump with an adjustable pump with a max flow rate of 520 ish gph (I can’t remember the exact number off the top of my head)
For the 125 I’m thinking I’ll do a 4 foot sump with some kind of refugium and obviously a higher flow rate than the 75. Plenty of bio media and mechanical filtration in both.
Id like to add that while I know there’s a lot of people out there who say you CAN put a lot of fish in your tank, and I respect the people who ethically achieve this, I don’t want any of my fish to feel overcrowded