I am not familiar with very many "drainage/overflow" models at all outside of a typical overflow?. I was planning on basically having just this inside my two drain holes (One with a 1.5" diameter)
Thatd basically be it for drainage as it'd be at the desired water level line.
As far as my understanding of herbies goes it just limits the drainage so that no air goes with it, thus lessening the sound? Is that it? I really am lacking knowledge on the design but am open to other options. I would like to keep as much tank space as possible though and feel like this design is close to as good as overflow boxes based on what Ive heard and Ive seen it in LFS's as well. Seems like a great design to save space in the tank and still oxygenate the water and skim the surface.