Backyard Aquaponics
A place to discuss aquaponics

I have been researching raft materials but I can't find affordable ones that are food safe. The next thought I had was a food grade rigid plastic and having a fixed platform for the net pots with a constant height of water. Has anyone tried this or think it might work?

Charlie gave a bunch of links in this thread that should give you some ideas - http://www.backyardaquaponics.com/forum/viewtopic.php?f=13&t=28109&p=548143&hilit=raft#p548143

I use multi-cell acrylic roof sheets as a 'raft' that sits across the top of my DWC and have clay filled net pots such that the bottom of the pots just touch the water (clay wicks a bit). Works well. The 'air gap' is referred to as the Kratky method and is an alternative to floating polystyrene rafts. Makes it easy to keep excess light out and no polystyrene issues.

mostly the issue is sag. So really depends on the span and the material.

depends a bit on how big the setup is. The air gap reduces the need for airstones within the DWC but still relies upon aerated water circulating via the pump etc. (so its a Kratky DWC rather than his non-circulatng system which is another one of the many things Kratky published - works fine with timer F&D).

If you have a large system that relies a lot on filters rather than media one drawback is you don't get the raft surface area.

the rigid plastic does not have to be food grade. Just inert and not coated in any chemicals etc.
acrylic and polycarbonate are pretty safe as is most HDPE products.

Charlies post in that link Scotty mentions is pretty comprehensive coverage of various options...

Thanks for the incite! I think I am gonna have to stick to a food grade plastic as my system is gonna start off outside with out greenhouse. I am afraid that rain will run off the plastic into the tank.