over 500 total sold!has to be the best!!!![ !!! IF YOU LIKE THIS PRODUCT,TELL EVERYONE WHY WITH POSITIVE PRODUCT RATING. BEST DEAL ON EBAY AND OVER 300 SOLD!!!!! 30 POUNDS OF SUBSTRATE , AWESOME BLACK 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.!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! YOU CAN’T BEAT THIS DEAL !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!   FORMULA FOR AMOUNT NEEDED 1 LB PER GALLON OF WATER FOR 1″ DEPTH. !!!!!