Wish I was a little more patient to wait for a response. I already have the sub in and sprinkled a light dusting of clay on the bottom.

So, I have about 1" estuary mud (scooped up right next to a mangrove), then 1" mud - aragonite - silica, then capped with another few inches of silica in two grain sizes. 2.5" total up front and 4" in the back. I'm going to add a little shoal and manatee grass to the back corner, then Oar grass in the mid to front. I just hope a 4 x 48" Tek light is enough for those seagrasses in a 30" tall tank. Fingers crossed.