Calgary does have some of the best water in North America, I have a close friend that used to be in charge of monitoring water quality in Canada and the US for a major company a bit back. I always used RO water in my main display tank, and my office tank that got filtered water had more algae problems.
Thinking back the reason I got started on it really came down to others who had nice setups making a good point, do I want to risk it and then have to battle the possibility of algae and other problems, or try to nip it in the butt before it appeared.
On my current tank I have moved to a RODI unit, and there are many great ones on ebay at a reasonable price now a days. I am going on over 600 g through my current one and it is still showing 0 for tds after running it for a bit (it now shows 1 for Tds for the first bit whenever I start making water), as well as 0 for copper, chlorine.

Have a look here The City of Calgary - Water quality parameters

All that stuff is going into your tank without using at least an RO system. RODI would be better as I see your TDS is on average 177-294 according to the list.

Sure the #s are small, but I wouldn't want to be adding to my tank;
- aluminum, arsenic, cadmium, chlorine, chromium, copper, fluoride, nitrites, nitrates ...
The list goes on :surprise:

We have similar stuff in our water here in the GVRD (my tap TDS averages below 10), and I use an RO system that takes it to 0 TDS.
Makes me feel better about my tank, even though I drink my tapwater :lol:

I'm assuming this is in relation to reef tanks? I use tap water in most fish only systems and it works just fine. I've used RO/DI for the last 15 years or so.

Yes full reef tank, although good to know about fish only.

My TDS runs about 8 to 10 so, I use it for my top off only.

For my 55 gal salt mix, I add Prime or Amquel to get rid of the chloramine. BRS did a study and it found that almost all brands of carbon did pretty much nothing to take out the chloramine, which can be deadly to the livestock.

It seems the results are quite in favour of using it, although I wish more local people would chime in.

You don't need locals to chime in, lots of people in Calgary use tap water. It's fine, almost always. It's "what if" you need to think about. Or, you want the absolute best you can get and don't mind spending a couple hundred bucks. Can you run a reef without RO? Sure. Will it be fine forever? Ya, likely. Will something in the water kill all your corals one day? Could happen :) So you decide how much risk you're willing to go with.

Use RODI
 

...but wouldnt it be nice if we could keep the Calcium and hardness of Calgary water!

I'm in deep SE Calgary. TDS is high 200's. Sure go through DI resin fast. I found I need dual DI canisters to get my TDS down to zero.

Keeping my spent DI resin to recharge once I have enough to make it worth the hassle. See how well that works.

I live in NW Calgary.

I always have used RO (2-5ppm tds) or RODI (0-1ppm tds). I didn't see a difference.

My tap water right now reads over 200ppm tds.

Hope this helps

I used to raised/bred Discus, the most sensitive fresh water fish that you could ever keep. Most discus keepers use RO/DI as discus is very sensitive to Chlorine and Chloramine, however based on my experience water here at the Lower Mainland is almost pure and Chlorine is the only thing that you need to watch out during Winter/Spring months.

A pinch of Prime during Winter/Spring time is all I use.