Instead of letting my Rock wool sit on a bed of Hydroton (or be buried in it) Im going with a white Poly that I clip over the Flood Table. "X"s will be cut into the cover where the stems and leaves will stick out. But the water will be protected from the light giving the roots the dark and moist conditions. The thing is that I'm worried about fungus. With Dark humid conditions under the cover after flooding. Question: Is there any reason that a bed of Hydroton would decrease the risk (either under the rock Wool or over or both) of Fungus or rot? Or any other problems I might not be seeing?