It's not a sump, it's a fug/algae scrubber concept.
You know, I went through hell for that bulk head. I originally went to home depot, because I read somewhere that they had them. Well they didn't and they had no idea what I was talking about. Then I went to a plumbing supply house and they had no clue, and I even drew it out for them. Then I went to a pool supply place, and after some thorough explaining, knew what I was talking about and had one; 2 1/2". they call them through-wall fittings, and I guess they use them for pools/hot tubs and such.
Good luck finding one!
I'm setting my fuge up with rock, sand, water today. Kind of psyched!