Great questions! This is my first time trying to colonize and fruit in a flood and drain grow bed. The bed has a geotextile barrier over grow media so that it floods about two inches over the barrier layer. On top of the barrier layer is a bulk substrate layer inoculated with Florida oyster mushroom spawn. During the spawn run, the bed is drained and with flood and drain turned off. My thoughts were that the mycelium would not colonize a flooded substrate. After the substrate is fully colonized and starting to pin, will turn on the flood and drain so that that bottom two inches or so of the colonized substrate get flooded and drained, about 12 times per hour, for one minute each flood cycle. I'm thinking that the mycelium will wick up the water to maintain sustained fruiting without having to soak the substrate.