I knew nothing of pH and hardness when I started, but kept barbs and danios without any apparent problems. The water where I was back then, (Richmond, Surrey, England mid 1960's), was hard and alkali, I don't have figures, but from the scale in the kettle, it was obviously bad. Of course, it is not ideal, but the likelyhood is that the shop you get them from, if relatively nearby, already has them in whatever you've got.