Its a 30g sump that I have used for my reef for a couple of years. I cleaned it up and now want to utilize it as a sump for a 100g freshwater tank. I am transferring my fresh 65g into the 90g. I have a Rena XP4 runnning with a load of media that I can move into the sump. Not sure where to put stuff....pot scrubbers? By the way, the skimmer is just for sizing. Its junk! Also the tank can be sun around so the baffles are at the other end. The drain from the display tank is on the left. So, the flow will be from left to right.