Denitrification Catalyst 5pcs for Maxspect Anaerobic Block

For optimum efficiency, it is recommended to change the denitrification catalyst every 2 months and the Nano-Tech Anaerobic-Block should be cleaned or replaced every 6 months. However, when cleaning or replacing them, DO NOT change them all at once. Clean or replace only half of them so that there are enough bacterial colonies left to grow in the freshly cleaned or replaced Anaerobic-Block.