Reverse Osmosis Water - per gallon

Most reef aquarists use artificial seawater mixes, and these always need to be made with freshwater. Likewise, all reef aquaria need their evaporated water to be replaced with freshwater in some fashion. Consequently, all aquarists need access to suitably pure freshwater. Unfortunately, tap water often contains contaminants, including chlorine, chloramine, copper, and a variety of other undesirable compounds, that make it unsuitable for aquarium use. There are several ways to purify tap water to make it suitable for reef aquaria, and the best method for achieving this is likely the combination of reverse osmosis and deionization (RO/DI) purification.