You can use your canister, no problems there. The only thing to make sure of is to remove most of the filter pads (keep a bit to hold the media in). Whats keeping me from using my canister is it is soo big and bulky plus a lot more work to clean then a simple reactor. I would not recommend a canister for biopellets though. Wiz.
Most canisters are not flow adjustable to keep the biopellets tumbling and also many are not clear (closest to this are magnums or eheims) to view the media.
My Filstar is clearish, but I see your point. Just trying to figure out a way to save some money. I have a perfectly useful canister, and since no one will buy it, I'd like to put it to good use.