Time to replace the water filter.
Please replace it every 50 to 100 diving, or replace immediately when breeding traces of bacteria or dirt adhered from fingers can been seen.
It does not contain any agent such as an antimicrobial agent in a sponge as it preserves water to moisturize beathing air. Therefore depending on handling and storage condition, the breeding traces of bacteria or dirt might be seen even in a few diving.
It is recommended to always carry and posses a spare water filter.