I have a refugium sump combo. Here's how mine works... I have the intake side, where the water comes in through a pile of live rock and gracilaria algae (my living filter sponge, in a sense). The protein skimmer is on this side, it skims all incoming water. Then, the water is forced through a series of baffles that go above and below the water line, one set high, one low, one high, with a good 4 inches of overlap, this acts as a bubble trap and also serves to slow the flow of the water before it enters the refugium. Then the water is drawn across the refugium, which I have bracketed by two pieces of acrylic so that if the sump is drained the refugium still holds its own water, protecting my pods
, macros, snails, hermits, worms, etc. Then the water goes through one more baffle, and there is the empty pit where my return pump is. I run a 20 gallon sump under my 58 show tank with a Mag Drive 9.5 this way, with no problems at all. My next project tank, the 135, is going to have a 75 long sump under it, with two refugiums, one with DSB
and macro, the other with miracle mud and mangroves. This, in theory, would make skimming superfluous, but I prefer to run the skimmer. I'll have the skimmer, a 600gallon rated high pressure skimmer, running on the intake, and I'll have a Gen-X 55 high pressure pump as my return. I like running my skimmer and return on opposite ends, it cleans the water up before it hits the refugiums, and then there is plenty of time in the refugiums for pods
to migrate if they wish. I plan to leave my refugiums interconnected with a 2" drilled hole, to facilitate pod movement. This hole will be high enough that they won't drain entirely in case of water failure though. Of course, I like to look at my refugiums, so for me this choice is as much a matter of aesthetics as praticality... I have a small house and I like having little nanos under my big tank.