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 suc

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).