Thats basically what iv had since I started doing this. Canister pumps water into one end, and it dumps back into the tank at the other. Filled with lava rock. I just dont have floating plants.
River mud is that ur max water flow? Looks kinda low. Unless duckweed is your goal. Iv read 250-500gph is ideal for plants, to fast and the plants health will suffer. I could be wrong so who knows.
Im in the middle of making a better container, will be 3 parts (easier to move when I move again haha) So the big box will be the highest, the long middle will be in the middle, and where it dumps back into the tank will be sitting almost on top of the tank. I am even toying with the middle box having a viewing window so I can somehow see the roots. Gonna use some neoprene rubber paint to seal it. Maybe by january it will be done