I'm on Oahu. The water is hard here, after filtering through the volcanic rock for many year. Quality is very good. Chloramine is not used here, and Chlorine concentrations appear very low. I have not been treating my water, even with pretty big water changes. That seems to have worked well for several years. I know several others who don't treat as well. Recently I had some deaths however, so now I am questioning everything I am doing. What are other folks on Oahu doing?