my current 30 gallon fuge is the middle compartment of my sump and gets all sump flow, which is ~900gph. therefore it is a high flow fuge... its a compromise like my entire system.
I have a 1/2 inch of miracle mud (2008) then 6inch DSB then 2 inches of loose rubble rock above that... I shoulda revived the mud a long time ago...too much work
Im growing macro and mangroves. the mangroves took a long time to get established, like 6 months, during which time they sent roots all over the place. Im not sure how much nutrients they pull out, but they look pretty. You should have some air space above the fuge to let them grow out. You also have to collect their fallen leaves before they breakdown or circulate in the DT...
In terms of macro, Ive tried several cheato and many different species of calurpa before they were illegal (everything is illegal to own in this communist state!). Most of the calurpa outgrew then overgrew cheato within 6 weeks. They also had fascinating morphs and colors, not just a big ball of spaghetti Too bad, you new aquarists dont know what your missing. As a safety, Ive always had a ORP meter. When I harvest the macro it goes into my mulch pile (worms!!!), and eventually under my wifes plants...