I am trying to find out what depths people have their beds set to and where I can get gravel in Florida that is reasonable in price. We have been looking at one foot deep and the prices for gravel are astronomical.
To save TCLynx from self-promoting or being accused of spamming... she has developed and sells a great index valve. It is the only one I am aware of that is specifically made with aquaponics in mind. The cost varies based on the number of outlet tubes and pipe diameter.
Suggestion - get more outlets than you currently need to allow for adding beds in the future. The additional cost is minimal and you can just route the flow directly back into your fish tank or just cap it off.
Seeing as Louis is in Florida, I would be the best person to contact about valves. I can't claim to have Developed them but I have worked heavily with the people who did and I can say that I was involved with the development of the "gravity modified" Versions.
There are other people selling the valves and you can find your distributor by using the Map link on this page
I can help anyone get in contact with the appropriate distributors for the Western Hemisphere and the Eastern Hemisphere you can contact http://www.freshbynature.com.au/