[tmoullet]

Why did you decide on a two tiered system? I've seen aquaponic setups where the farmers are using a floating medium above the fish pool.

[ph0rque]

It's hard to find a 12" (30cm) deep medium that would allow for fruiting plants such as tomatoes, be lighter than water, and not just be a support structure such as polyurethane foam (i.e. not having roots grow through it).