6" sandbed and pack the rest with rock It worked wonders on my 75, I am going back to that style setup. I just cleaned out my 29 and reinstalled it under my 200. I have always ran slow flow through it, and I also have a skimmer in it. It may sound crazy that I just put it all in a tank, no baffles or anything, but the proof was in the pudding. That tank was pretty much unstoppable! Ireally enjoyed how simple of a setup it was, so emulating it is all I can think to do again. To me all of the excessive baffles and stuff just take away space. Pack your return under some rocks and you won't need a prefilter either. Clean it every 8-12 months and clear any tiny snails or rocks that may have gotten caught in it. You can even hollow out some space for macro. Sincerely I felt it was better than anything else I have tried to do, and with less maintenance. K.I.S.S.