Penn Plax Cascade Pro-Z Canister Fliter for Aquariums, 2-Pack

Why is this item not part of subscribe and save? The pro-carb filt a pack is.

Can this be used over and over again? Or would it have to be changed during maintenance of the canister filter?

Is this a biological media or a chemical media?

Can you use this in a 1000 series if so how would you set up the 3 trays