Api Nitra-Zorb Size 6 Aquarium Canister Filter Filtration Pouch 1-Count Bag, Model:110A

API BIO-CHEM ZORB - They are much better that activated carbon. They keep odours away . They can keep cloudiness also away. But clearing up of dust particles is not there job. They have longer life - 2 months ( atleast double than activated carbons ) . If your canister filter is big , you might need two to cover the entire area, but in this case may be you can use it for 3 months (depends about overall aquarium situation and volume )API NITRO - ZORB - Very handy when you have ammonium , nitrate, nitrite Spike. I had a massive spike of all three of them- Ammonia above 3 PPM, Nitrate to 160PP ( thats max it shows in test, not sure if it went above that ) . I have two canister filters. Kept one in each of them . Surprsingly Ammonium came to Zero in 24 hrs. Why am surprised is because Seachem Prime i was using for almost a week without much progress. With Nitro-zorb, Nitrate was not going down even after 48 hrs, so i wrote to API. They said "many recharges needed to control Nitrate spike " . So i waited - after one week it dropped to around 80-90 ppm, after second recharge it reached around 30-40 PPm and after third recharge it became zero. It works better than seachem prime for these kind of situations is my take.