There are pretty much 2 options, DIY syphon and HOB
If you dont want to build you can go with something like this
, and I would suppliment flow with a CL
system, maybe even with a SCWD.
Or you can get the same CPR box rated at 600gph and T it off for 2 returns and add a powerhead somewhere if needed depending on what return you use.
Are you looking for FOWLR