Or raise the filter and have gravity feed into GB..
Many ways to skin this cat
Looking forward to your progress
Yep, I thought of that too. Only downside is that if I do that, I won't have a constant height in the fish tank because it will still fluctuate..........Unless I do an overflow to a sump, then sump to the raised filter, which gravity feed to the beds as you mention. Sort of a hybrid of all these ideas into one. Decisions decisions!
A venturi siphon in your FT will keep it at a constant level. It will not fluctuate and it will get the waste off the bottom as well.
But to do that would require you to drill a hole in the tank at the level you want the water to exit, correct? Or is there a way to do it without drilling holes (a la a PVC overflow which somehow pulls from the bottom of the tank instead of the top)?