Bio-Lux is an Ultra Porous Ceramic Bio Media, Bio-Lux 4 pack that can hand the biological load for a 50g aquarium. Each piece measures 6 3/8" x 1 1/2" x 1 1/2". Increase in beneficial bacteria for nitrification and denitrification. Removes harmful Ammonia, Nitrites and Nitrates. Decreases aquarium maintenance- fewer water changes. Stabilizes pH between 8.0-8.4. Each box of 4 contains over 43,000 sq ft. of surface area for beneficial bacteria growth. Bio-Lux is a superior media for holding bacteria and is suited for Saltwater and Higher pH Freshwater tanks. Bio-Lux is extremely hydrophilic and is extremely good at retaining moisture.