Black Diamond is a media blasting material. As the name indicates, it is black. It is almost a glass like material. There are different grades, which correlate to different grain sizes from really fine to a fairly coarse sand. It's inert and works well for me. And it is pretty cheap; I think around $10 for a 40lb bag. If you don't mind the root tabs, it's a pretty good way to go. I've had it for the past year or so with no issues. Just rinse it first and you should be good to go.
You could start it in a bucket with a fish-less cycle a few weeks to a month before moving. If you seed it by squeezing a filter sponge into the bucket, you may be able to cycle it in a week or so. You could then transport the fish and plants in the bucket(s) and help minimize the stress to the fish if it is a long move. Just lay a base layer in the tank and then transfer the substrate from the bucket as the top layer in the tank. The cycle, if there is one, should be really quick.