Filtration: Seachem Matrix Is High Porosity, Inorganic Solid Bio-Media That Provides Efficient Biofiltration For The Removal Of Nitrogenous Waste In Your Fish Tank Or Aquarium. Diameter: Measuring About 10Mm In Diameter, Each Liter Of Matrix Provides As Much Surface As 170 Liters Of Plastic Balls! Matrix Provides Both External And Internal Macroporous Surface Area. Macropores: These Matrix Macropores Are Ideally Sized For The Support Of Nitrifying And Denitrifying Bacteria, Allowing Matrix To Simultaneously Remove Nitrate Along With Ammonia And Nitrite In The Same Filter. Matrix May Be Placed In Any Kind Of Filter And Is Particularly Effective In A Canister Filter Country Of Origin : United States