I am building a sump using a 20gal long tank. The tank measures 30Lx12Hx12w. My in flow area with baffels is going to be 8Lx7Hx12W at one end and the refugium is 9Lx9Hx12W at the other. With what is left over for my return pump section. My question is does this sound like a good design. And with the small size of the refugium is it really worth having. Now as a real noob question why would I even want a refugium and what is its purpose.