The quality of fresh water use for salt mix is essential in the success of marine aquarium keeping. Raw Water (Tap water) containing too much chlorine, heavy metals, and impurities (NH4, NO2, No3, PO4 etc…) which are harmful to coral and marine fishes. RO/DI or DI unit water purifier is probably the most practical and cost effective option to process tap water into high quality pure water for salts mix, to perform peroidical aquarium water change and as fresh water top-up due to evaporation.
Reverse osmosis (RO) is a process which purifies water by pushing raw water through a porous membrane, which leaves 95% of impurities behind as rejected water. Ion exchange resin is highly recommended as the final stage on a reverse osmosis unit, the combination can produce ultra high pure water.