[Apophis924]

Yep thats them a green canister and it turns dark blue when exhausted. I still use it. No complaints. just that there is no advantage to using two in series for cleaner water. Using one canister works great for me. The chemeicals i test for show up as zero, My tank is doing great. The things do work. But using two in series is akin to using two vacum cleaner bags to get a cleaner carpet. I do recommend them, i tested water before and after using the filter and the claims are true at least in respect for the chemicals that i can test for.