Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Why not just go with EC? It is black, and looks pretty good, IMO. Or, if you want fine, just go with sand. Enough to come above the rim a bit in the front, then a couple of inches deep in the back. Rocks or driftwood to hold it in place- these will tend to settle down and end up level.
Adding a finer material over a coarser won't last. The sand will sift though the larger pieces and end up on the bottom. Granted, this will take time. The more you disturb it with transplants the faster the materials will blend.