I was lately searching for suitable( for me...) aquarium gravel, which would serve me as a total substrate, or to cover Turface, which is waiting for it.
In Florida, between Orlando and Daytona Bch. I searched seemingly every store to no avail, so I decided to search for it on the Internet. This led me to producers of water filtration gravel (
http://www.redflint.com/filter_gravel.htm) - picture + grades table for orientation.
Through Clark Corp., this gravel is sold here by Coast Pump ( several warehouses in the area) in 50 lbs. bags for $10, which seems to be fairly reasonable. The one I purchased, 3/16 x 3/32 grade, is of a predominantly dark grey colour, which in water will be close to black.
I thought some of you might find this information helpful...