I built one out of a 30 gallon tank for my 92 gallon bowfront. What I did , I went to home depot and bought some acrylic. it was very cheap. I cut 6 pieces of it they were the width of the tank and like ten inches tall. those you use for your baffles. do them in sets of three. I divided the tank into 3 parts. from left to right, skimmer, return pump, and refugium. Say your tank is 30 inches long, what I did is I used 8 inches for the sump and the return and 14 inches for the refugium. this worked well for me and like dakar said anytime you can increase the total volume of water the better. And not to mention it makes the display tank so much prettier without the heater and all of the power heads being visible. Good luck