Bulk Reef Supply is amazing to work with -- excellent shipping to Canada, and they're much more upfront about how they source their Ca, Mg, and alk products than regular aquarium companies.
FWIW, I think it's cheaper overall to use calcium reactors on big tanks than 2 + 1 part solutions, but I'd always have a bucket or two of their products around for quick corrections of water chemistry. I'm also a fan of topping up with kalk (I like how it tends to drive pH up), but I realize it goes into and out of style cyclically, and we seem to be at a low point.
FWIW, I think it's cheaper overall to use calcium reactors on big tanks than 2 + 1 part solutions, but I'd always have a bucket or two of their products around for quick corrections of water chemistry. I'm also a fan of topping up with kalk (I like how it tends to drive pH up), but I realize it goes into and out of style cyclically, and we seem to be at a low point.