There are a few reef stores near the airport or at least close by if driving. There is the store on Queensway and Kipling called Ocean's Alive, thats about a 20 minute drive from the airport using local streets depending on time of day and traffic. Another one close by is on Torbam St, just south of Steeles Ave, its in a strip mall, forgot the name, they have really nice selection of corals right now. Has most SPS of all the stores in Toronto I think, and even some clams.
Then there is a Big Al's Aquarium Services outlet on Dundas St, which is probably 20 minute drive as well, good selection of marine fishes, but their coral stock right now is lacking.
Another one that is in an Asian strip mall right beside Big Al's, that also sells house plants as well, good selection of corals, not as much fishes, but prices are higher than others.
Thats about all the stores I think around the airport area that is within 30 minutes drive.