cant use it with soft bellied fish like cories, sand is made from glass.
you will also have to get MTS to move the sand around to keep it from getting gas pockets in there that may kill your fish
you can use pond filter sand though, a lot cheaper than buying it at lps
but 50lbs maybe? someone else may have input.
black sand would look very nice imo and id do it if i werent planting my tank