I say yes, i even put salt in my collecting buckets, I generally use about one cup sodium chloride to 50 gallons of water and about 2 cups of calcium chloride per 50 gallons of water. I use rain water to replace evaporation, and through partial water changes you can slowly decrease the salts content over time if you wish but i generally keep close to those concentrations all the time. Even soft water fish will do well like that, they just won't be able to breed, of course there are exceptions so know your fish before adding it to your tank. I'd like to give a shout out to quarantine tanks, always use one, keep it on at a higher salts content that the main tanks.