Pot scrubbers would not be very effective in a canister (not as much surface area as in lava and other porous material). For a submerged application like a canister you need to maximize surface area. Several options here: manufactured media (from Fluval, Eheim, etc.) or DIY lava gravel is what most people choose.
Scrubbers do a good job in wet/dry applications though (they allow water and air to mix pretty well without becoming clogged up like lava would).