World Wide Imports Nature's Ocean Marine Pre-Washed Atlantic Crushed Coral #8 20 lbs

Benefits of Nature's Ocean® Reef Sustrates:
•100 % From The Ocean Floor
•Natural crushed coral sand
•Maintains superior pH and marine chemical balance
•Provides maximum surface area for biological nitrification
•Scientifically graded for uniformity which provides maximum
  water flow and aeration
• Prevents anaerobic (Dead Spots) in Bacteria bed.
•Completely chemical free
•Pre-washed (minimum rinse required)

Recommended:
Use at a rate of 10lbs per square foot of the tank floor's bottom area which yields about a 1" deep covering. Depending on your needs or preferences the depth may vary from 1/8" to 3"s of covering.

Grain size:3.5-5mm