Backyard Aquaponics
A place to discuss aquaponics

ralath,I can probably help a fair bit ,I raise 10's of thousands of Tilapia every year ( in Thailand) and am currently nutting-out of system for growing lettuce etc. My start system will be around 800 square metres ( ahh a metre is a bit over a yard)but the priciples of what is required will be similiar.I'm looking at a large gravel bio-filterflowing out into a floating raft system.
Elkaybee is correct about lettuce,I have no bitterness problems growing it in summer in Sydney Australia but theroots are kept cool with mulch.

I tried googling weather conditions for North Carolina but great variance depending exactly where in NC you are.

Hi Ralath, maybe google about planted (or "vegetal") walls, that could be an option for planting lettuce as well. Might make more sense for lettuce as you could have a lot spaced close together. They have one at Epcot in Orlando, it has lot of lettuce on a not-big wall.

Been looking at PVC prices today and sewage pipe is a lot cheaper than schedual 40 pipe. Any reason not to get sewage/drainage pipe? Also end caps for the pvc are kind of expensive. What are some alternative ways of closing the bottom? Would have to be something strong enough to hold the weight of all that gravel in the pvc tower....

Ralath

Ferrocement is just normal cement (not quickcrete) mixed with sharp sand (usually 3 sand to 1 cement ratio) plastered onto metal mesh.

Critical fact in water pressure is depth not length or breadth.
Link to vid below should give you some idea of the technique.

http://www.youtube.com/watch?v=U7IGsG0TzUo

Gave some thought a few years back when doing hydro re vertical (well sort of) beds. Idea was to have a central vertical pole with horizontal poles running off it in a spiral. Using non slotted draincoil supported by the horizontal poles spiraled down. No media, nft with net pots. Didn't get round to doing it at the time, but might be worth a thought. Problems heat and getting the pitch right (and the usual with NFT, pump failure).

what's the strength like on the ferro-concrete? That video shows the process easily enough but that only looks like maybe 100L. What happens when you move up to the 1000-5000L range? Is it sturdy enough? We're in the process of planning a 3000 sq/ft test farm and I'm exploring the idea of concrete raceways for a raft system. Just curious of savings of concrete based raceways vs wood.

You can order different strengths from concrete suppliers.I'd recommend consulting a cement company for an idea of what blend is best. No reason to gamble on a large expense item like a raceway for fish.

Haha i never thought after a long backround skulk,that my first post would be an answer not a question.....
The problem with such a long bed that i can imediatly see is expansion/contraction....i biuld koi ponds and we have to be very carefull over long distances to allow enough flex....HOWEVER that mesh system is the strongest most flexable of the diff construction methods....
My my other comment would be leaching pushing up ph.....not sure if this is a big issue due to use of buffers etc......somebody else?