RO/DI. Water is the single largest ingredient in a reef system and everything depends on its quality and its stability. Spectrapure is by far the best choice with about 30 years in the industry and in this hobby, If you could lay your hands on some old FAMA magazines (Freshwater and Marine Aquarium) from the 1980's you would find their ads in there and they have sponsored many reef forums for decades. Don't forget a good handheld TDS meter to monitor the RO/DI systems condition.


oh and test kits get a decent water test kit lol

