System Expansion Plans

OK...So, I've been toying with the idea of expanding my Aquaponics system to include DWC raft beds. I threw together a little sketch in Google Sketchup to show what it may evolve into later next year. I already have some of the peices needed such as the AquaTop AB120 Blower, Expanded Shale, etc. After careful calculation I can probably throw about $1.5K at it, which would include a Hoop Style Greenhouse covered in 6mil Poly Greenhouse plastic...not bad for the extra I would gain in grow space. I can use the existing system along with the two Danner MagDrive 9.5 -950 GPH pumps that currently sit in the fish tanks along with the Expanded Shale growbeds and the dual 1000W Titanium Aquarium heaters. I can redisign this system into a Constant Height in Fish Tank with no Sump needed. Using an Undercurrent model the Raft beds would be the sump with the pumps sitting outside of the tanks/growbeds while pulling the water through the  DWC raft beds and pumping water backup into the Expanded Shale growbeds. From my calculations even if all of the Shale growbeds filled at the same time/rate, then the rafts water levels would only drop 1.5 inches or 3/4 inch if I installed an indexing valve. The combo Vortex / Swirl filter and degassing chambers along with the shale growbeds should take care of all the filtering for the system. On the Mag pump with a 3' head, I should get about 800GPH out of both pumps , that would circulate all of the water in 4 raft beds in approx. 1hr 19m. The Shale growbeds would flood and drain approx. 3 times per hour.  Taking all growbeds into consideration, initially I will have 345Sq ft of growbed space. Using the assumption that you need .3LBs of fish per square foot of growbed space, I would calculate that 103 +/-  1Lb fish are needed for the system, approximately 25 fish per 175 Gal Tank.  I have the capacity to add another 2 Raft growbeds and up my count to 150 fish total.  Here is a quick fly by of the system.

 

DWC Raft beds are fed by 2" PVC through to the water pumps. Media grow beds use standard 1" PVC drain pipe and 1/2" PVC fill pipe with ball valves for flow control. AquaTop Blower uses 1" and 3/4" PVC pipe with flexible tubing feeding 6" air stones every 3ft in the Raft beds and 12" air stones in each Fish Tank.  I have calculated a need for approx. 6CFM total for the system @ 10" H20, and 2CFM @ 24" H20, which the AquaTop AB120 should provide.