CHIFT-PIST is the design I use ( see Wolfracers system) . I maintain the level of the fish tank by a 1-1/2" overflow to the sump. My feed line to the grow beds runs clear to the bottom of the fish tank and is 1-1/2" I also have a tee with a pipe running above the tank to prevent the feed line from siphoning out the tank. Gravity feed to the growbeds, believe me I pull plenty of solids off off the bottom.

This has worked well until my fish got to the size they are now. I have also sort of crashed my system by pulling out plants and replanting with herbs and it is now recovering. Nitrates never got really high and the nitrites were still 0 but I do have lots of solids and murky water. Good thing catfish are tough. I am adding a swirl filter to the system today and will post pictures.