Quote Originally Posted by keith_r
i appreciate your reply Oliver..
i'm a member of several forums (aquaponics, ponds etc) and try to learn as i go.. i was at a presentation for a guy selling systems, everything was galvanized, fish tanks, gb's.. and when i questioned him about it he stated that he'd been doing it that way for years with no issues.. on another forum i follow someone experienced some fish deaths, and had galv tanks (not lined), after this happened to a couple people someone got the smart idea to have their water tested and found toxic levels of metals that had leached from the tanks..

on the byap forum they are trialing 3 growbeds side by side from one ft, one is cf, one is flood and drain and one is timed flood and drain, the cf bed has been showing better performance of all but a couple of plants, it's easier to follow a recommendation when there is visual proof..

your point about DO levels has been demonstrated on many forums.. gb depth though, i've seen great performance out of "shallow" beds and planting things that don't need the depth, but personally i think deeper would be better, there's a system of one of the members here (TCLynx) that is using rubbermaid totes for gb's 20" deep, these aren't being "completely" drained because she drains out the side, again she shows tremendous results..

i take pretty much everything i read with a grain of salt, but with a well documented system (pictures/dates etc), including failures/issues etc beats the hell out of a verbal argument every time

i'd be interested to know how you arrive at that stocking density as well...
I don't think there's a "one size fits all" type AP system. There are SO many variables you can't just say what works best for someone in California is going to work for someone in Florida. The type of plant, climate, and many other conditions can affect exact performance. I'm not saying anyone is right or wrong, but rather what you find what works best for you, well... works best for you!

On the depths of the grow beds, I just learned today that the commonly held belief that a tree's root system mirrors the branches above is NOT true for Florida planted trees. They tend to spread out far and not deep, often times 3 times the length of the branches. This is because the roots simply don't have deeper soil to grow into... similar to shallow grow beds. Sure, we can discuss the microbes and so on and so forth, but I just want to point out that with evolved multicellular life forms, they tend to have advanced mechanisms for survival. If anything, it is a bit arrogant to believe we know best given our tiny amount of knowledge for all circumstances when there are more variables than there are facts or answers. Trail and error is the way to go while using what we do know as a GUIDE and NOT GOSPEL. Plus if it doesn't work out, you can rack up kills to become a REAL fish farmer, right?