It is pretty much impossible for the average fish keeper, let alone an experience fish keeper, to tell the two species apart in almost all cases. Where the gars were from is usually the easiest way to determine if you have a Florida gar or a spotted gar as Florida gars are more commonly found in stores & online because they're farmed in large numbers while spotted gars generally are sold by those who manage to catch them. Also, if you're outside of the United States, then your odds of having a spotted gar drop dramatically as very few, if any, have been exported from the U.S. although it is possible that you could have obtained one from within your country since you're in Canada.
However, there are two people (E_americanus & Polypterus) on here that certainly can help you out & ID the gars for you, so please post pictures of them in the "ID My Gar" sticky.