Nature's Ocean Bio-Activ Live Aragonite Reef Substrate 8LBS (Grain size: 1.0 -2.5mm). Premium Live Aragonite Sand for Aquariums; Collected in its natural environment and packaged in its natural state (U.S. Patent #'s: 6,376,299 & 6,939,708); Just place in tank, add saltwater (for best results use Nutri-Seawater) then add fish, no waiting required; Instant ammonia cycling; Perfect for under gravel filter For Best Results Use as Follows: Use a minimum of 1 pound of Bio-Activ Live Aragonite per gallon of saltwater. Setup filtering system and allow it to circulate. During the first month, introduce no more than 1 inch of fish per 5 gallon of saltwater.