purigen

Ok, 55 gallon freshwater tank with a Fluval 305 Canister Filter on it. In the filter I only use ceramic noodles for bioloigical filtration and purigen. I have 4 bags of Purigen. I have 2 in the filter and 2 on standby. The Purigen has been regenerated 3 times. So, here's the odd issue... I...