I'm using an old Fluval 203 with a couple bags of carbon, the same carbon from Brents group buy. If you use a canister be sure to remove any of the sponges and also change out your carbon often.
Regarding Phosban reactors, they also make good second chambers for calcium reactors.
I wouldn't recommend using a filter sock. You don't want the carbon to roll around and grind into particles. You could however place the carbon in a fine mesh filter bag and drop that in your filter sock.