Reverse osmosis (RO) purified water is produced by passing tap water through a semi-permeable membrane that removes virtually all dissolved minerals, chlorine, and contaminants. The resulting ultra-pure water has a TDS of near zero and a neutral pH. RO water must be remineralised before use. For freshwater: use Seachem Equilibrium to restore GH and KH. For Malawi cichlids: add Seachem Cichlid Lake Salt and Malawi Buffer. For soft water species (Discus, Cardinal Tetra, Crystal Shrimp): add only a small amount of remineraliser to achieve the very low TDS these species require. For marine: use a dedicated marine salt mix. RO removes chloramine which is not fully removed by standard dechlorinators. Related fish: Discus, Altum Angelfish, Cardinal Tetra, Electric Blue Hap (very different water needs illustrating why RO is essential).
