These blocks are 12” x 12” x 2” thick and have thousands of pores that allows water and air freely flow through the blocks. The walls of these pores are where the nitrifying bacteria colonize and convert ammonia to nitrite, and nitrite to nitrate. The total surface area for the bacteria to colonize is mind blowing when compared to other types of media available. While there is no way to be 100% accurate in surface area calculations on this type of media you ca be safe to assume around 50,000 square feet in one cubic foot of media (six blocks).