The Maxspect Denitrification Catalyst Refill Pack for Nano-Tech Anaerobic-Block (5pcs AB-C5) is designed to enhance nitrate reduction in aquariums. Each catalyst piece boosts the performance of anaerobic blocks by promoting beneficial bacterial growth. This improves water quality and clarity, maintaining a healthy aquatic environment. Ideal for both freshwater and marine tanks, it ensures long-lasting, efficient biological filtration.