I've done several, because 1) I like the sound of trickling water and 2) I buy used tanks and I seem to aquire some with missing center brackets!!!
On my most recent I did a diy watching you tube the KING OF DIY. I wrapped sponge around light diffuser (the cube kind) and fit into a corner (like a triangle). Inside the triangle I put some lava rock, then I put a pvc
piece that went up and over the top of the sponge. Run an air stone down inside the pvc
and use a larger pump for lift. It will move the water through the sponge and up over the top for a waterfall.
I also run a traditional filter on the other end of the rank, because I prefer multiple forms of filtration.
I would really advise you look up the KING OF DIY on YouTube he has tons and tons of video.
Hope this helps, its trial and error really. One last tip... scale is important (to me) I put many smaller plants in the water, and wandering Jew and pothos in the filter. All plants but especially pothos will eat the nitrates and help the filtration.
I'm no expert. My tanks are forever a work in progress! Good luck, Rachel