I am trying to decide whether to buy an RO/DI filter before I do my first fill. Is this really necessary? I live in Calgary (but have just moved here from out east, so not sure what the water's like -- anyone know if it's safe to use Calgary tapwater in tanks?!). I wouldn't have dared to do that back in Toronto

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Also, anyone know where I could by a decent RO/DI in person, rather than mail order? I want to fill the tank this weekend, since I won't have much time for the next weeks to go much further. (Yes, I know this hobby is all about patience.....

).