Marine aquariums require absolute precision. Saltwater chemistry is unforgiving. This category covers the intense reality of reef keeping and marine fish husbandry. You must use a four-stage reverse osmosis deionization (RODI) system. Tap water will destroy a reef tank. We explain the exact mechanics of protein skimmers, wavemakers, and specialized marine lighting. You will learn the critical balance of alkalinity, calcium, and magnesium. We detail the complex nitrogen cycle within live rock and deep sand beds. Marine quarantine is mandatory. A single outbreak of Cryptocaryon irritans will wipe out your entire investment. We break down the dietary needs of specialized marine grazers and demanding corals. Stop attempting saltwater systems on a freshwater budget. It will fail. Read our detailed guides. Invest in proper testing equipment. Master the extreme chemistry required to keep marine organisms alive in a closed glass box.