[THIS IS NOT SILICA SAND, THIS IS RIVER SAND!!!!!!!!!!!] BEST DEAL ON EBAY!!!!!BETTER THAN WHITE, DOESN'T TURN GREY OR LOOK DIRTY AFTER AWHILE LIKE WHITE SAND, STILL LIGHT ENOUGH TO BRING ATTENTION TO YOUR AQUARIUM.24 POUNDS OF SUBSTRATE, FINE DARK TAN SAND. SUBSTRATE SERVES SEVERAL PURPOSES, SOME KEY TO A HEALTHY HABITAT.SUBSTRATE SERVES A ROLL IN THE NITROGEN CYCLE BY SERVING AS A WAY IN WHICH BENIFICIAL BACTERIA COLONIZE AND GROW.IN ADDITION TO SUPPORTING BACTERIAL COLONIES.SUBSTRATE CREATES A MORE NATURAL HABITAT FOR THE FISH.FINE SUBSTRATE LETS PLANTS TAKE ROOT AND CERTAIN FISH LIKE TO BURROW.ALSO GREAT FOR TERARIUMS, CRAFTS AND OTHER PROJECTS.   FORMULA FOR AMOUNT NEEDED 1 LB PER GALLON OF WATER FOR 1" DEPTH.