Hey, great build! Very unique concepts thrown together here, should be interested.
Regarding that extra pump and the question about circulation, I definitely think you need to add some water flow in the bottom half of your tank. The way I see it now, you have very little circulation in the bottom half of the tank, and around the rocks. You want more flow for nutrient export. Especially in all those caves you've created, the fish will probably be pooping in all those caves as if they were outhouses :P Normally with such intricate rock structures, people would build the rocks on top of PVC piping which they have drilled a million holes into, and plumb those pipes as returns from bulkheads at the bottom of the tank, so that there's water flow from within the rockwork.
That's my 2 cents on the subject.
Very exciting!
