I'm going to be making a 16" x 16" x 18" tall Nano that's 18G. I'm wondering what kind of circulation should I have in the tank for SPS? :-) In the back of the tank there will be a plexi partition, similar to an internal overflow. The difference is, there will a 10" surface overflow in the center of this partition with a surface skimming pipe that will go to the sump. There will also be slotted panels on the right (Red) and left (Blue) that will make up the 6" dif. (3" per side). These slotted panels will be slotted from 3" above the bottom to 1" below the surface. I will have an intake in the internal overflow for the (circulation only 550-600gph) pump that's underneath the tank and will return the water back to the tank from inside this internal overflow. This water will return from behind the internal overflow, then pass through the slotted panel, circulate around the tank and back through the slotted panel. This way water can whirlpool through the tank, back behind and then back to the tank, like a partitioned frag tank. Now i'm building something that can return this water to just the left side, or just the right side, or both sides at the same time. The question is how long should these returns be open for, a few seconds each, a few minutes each and then both, what should I do? Should it be first left (Blue), then right (Red), then both or what? Also above the tank there will be an other return from the sump that will be rated at 400-480gph.