That's because DD went to another forum. He explains it a little better, He moves the drain to the bottom and feeds from the top. I'm not allowed to link but google it. I would never have my drain on the same level as the feed unless i was nft or swc.
i'm getting a bit more confused about this.
regarding the bucket in the "10 lb test" . . . . he says (@ that other site, in part):
what you see hear is basically an undercurrent but i souped it up. room is 7ft tall hence the undercurrent style to keep the plant res's on the floor, not raised as mpb style. dds
but my original point remains the same . . . i don't see how you can achieve a bottom drain and feed at the top . . . . unless you are bringing the drainpipe back up (outside of the bucket) and create a weir. i've stared at that interior bucket pic quite a few times, and see only the two white bulkhead fittings and that yellow thingy. they all seem to be at the same level. do you see another down lower? if it works like a UC, then one of the white would be an inlet and the other an outlet . . . but they seem small for the flow that i assume he would use. are there other pics that show what's going on?