They must not use chlorine or cloramine in the treatment process, or all your fish would be dead. Chlorine will dissipate after 24 hrs with good aeration. Cloramine will not...
Chlorine is also used in variable amounts throughout the year and I believe I've heard of companies bringing in chloramines when they flush stuff out. Either way it's playing with fire, and is something you can combat pretty frugally. Though not all of us are as invested as others.
My opinion is just cause you have rays you think are "thriving" cause they eat a lot and just cause they might drop a litter here and there does NOT mean you aren't going to cut your rays life in half with crappy water. I sure as heck wouldn't assume everything is "fine" just cause they eat and breed. Take a ray that's hardy and drop him in a tub with a female and a bunch of horse crap and I bet he'll still try to breed with her despite the toxic living conditions.
Nobody has PROVEN that our tap water which is thousands of times harder then any water they'd ever be exposed to naturally doesn't have long term health effects.....
Fact is rays are new enough to the hobby and their life expectancy is long enough that we have no clue what the long term effect of our garbage water is on rays....
Best thing you can do is to try to replicate the natural environment your ray came from. For some people this means dumping any water they can get into their tanks and calling it good. Others will strip EVERYTHING out of the water and only add back what they feel necessary.
Any water will work - it's a matter of will it work for a year or 2 or will your rays tolerate it for decades?
