I have been doing a bit of digging through this forum and others for any user knowledge on vertical growing similar to the ZipGrow Towers that Bright Agrotech is using. I am interested in how one figures the amount of water needed per tower if it was planting with 4 or 5 plants (lettuce, herbs or other green like chard). Once I have an idea on the amount of water needed to run through the system, I am assuming that I could then calculate the amount of fish needed.

In my yard I have roughly 20 x 30 feet I can build a green house on that receives full sun year round. I am looking to start a small business that would allow me to sell through several successful avenues. While I initially thought to build a raft system, I like the higher yields the towers produce in the same amount of space. Any shared knowledge from experience would be great, Thanks in advance!

This is a complete guess but I would say 20% (or less) of the total volume of your towers will have water running through them. The rest is the ZipGrow media, roots, bacteria, and waste buildup. A good rule of thumb is 3:1 ratio of grow-bed to water. So take the total volume of your ZipTowers, divide it in 3 then you have the total volume of water. Divide that by 5 (if measured in gallons) and that will give you a recommended number for how many pounds of fish you can stock (again making an educated guess as to what they each weigh). Always err on the "understocked" side rather than the "overstocked" side! Don't try to max out fish production as your major producers are the plants anyway.