I have seen people suspend coated plywood over(could even be done with styrofoam i guess) over the top of DWC beds. I know this would factor a reduction in nitrification and would have to be considered to balance fish numbers and probably aeration and filtration to some extent. Some say there are advantages with this type of arrangement over floating raft.Can we discuss the advantages or disadvantages of this?
This could be a good alternative for small systems but not for commercial farms. I do not like the idea of suspended wood over the troughs for commercial systems because it would reduce the mobility of the farm. When I remove and harvest some rafts I can push the rest of the rafts down the line with one finger to open up the opposite end of the trough. I then place rafts of small plants in the opening. This would not be possible with suspended wood.
I do not think suspending rafts would decrease nitrification because the bacteria live in the water column. That is why the water is a tea color.
So i get from both of you Chris and Ryan that there is the ease(labor) of production, no shortfall in nitrification, and more efficient grow-out times when using floating raft.What about cost considerations?, as this may well be a factor for those considering commercial AP. I'm not sure,but fixed raft might save a little on aeration, foam replacement etc.,I hope to hear from our fixed raft people on this. As Ryan mentioned calculating the fish to raft ratio, maybe a good place for you all to put a rule of thumb on this conversion for floating raft?