to expand on KarlTH's post, the harder the water, the more likely a decreased lifespan due to organ failure from calcium buildup. they will adapt in that they will live, show their full color and grow, but will not breed. to help you can can use RO water to soften your water (RO will have virtually no TDS, and no measurable hardness, pure RO water with just a little tap water and peat filtration is pretty close to ideal for true blackwater species), however, RO units are not cheap. running peat in your water will also help reduce hardness and will create a blackwater effect which replicates their natrual habitat which will reduce stress and help bring out their color. while it will help to reduce hardness, its not going to reduce it by much and if you don't like the blackwater look you'll have to run carbon.
The much harder part with adapting cardinals is getting them to eat after transit. use baby brine shrimp for a day or two to get them started. don't overfeed but its like candy to them and they can't resist and thne you can transition to other foods.