Adding salt depends a lot on what type of water the fish have been bred in. Many fish have been bred for generations in fresh water so adding salt could stress them out. I would suggest adding a little bit of salt and seeing how they do on a low dose.
Im sure your not suppose to add salt to the tank if any of the fish are scale less, as it will can burn them. The albino cordora, is a scale less fish. As for trying to increase the chances of your fishes breeding are you sure if you have males, and females, if so good water quality and a varied diet ( live food especially) will bring your fish into breeding condition. And then let nature do the rest.