So I have done some research, and where I live the chlorine level in my water is 0.85mg/l (<1ppm), and 56 - 73 (mg CaCO3/L) . In addition to treating my tap water with a water conditioner, what is the real danger in using tap water instead of rodi. If i am being extremely silly here please tell me, and explain what the benefits/need of RODI is, if treatment of tap water is an option. Please also explain why this is a bigger deal when discussing saltwater tanks and not freshwater (I have no coral yet and will definitely use rodi when i get there).