100% from the Ocean Floor. Natural crushed coral gravel. 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: 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.