What is the recommended salinity for a saltwater aquarium?

Typically salinity of saltwater is measured in specific gravity and/or parts per thousand (PPT). The specific gravity of natural seawater ranges between 1.025 and 1.030, depending on the location from which samples are taken.

For a fish-only saltwater aquarium it is considered acceptable to keep the salinity between 1.018 and 1.026. The lower end of this salinity range is what is referred to as hypo-salinity and is used by many hobbyists to combat and control many pests and illnesses that ail our beloved fish. Although hypo-salinity is a common practice in quarantine tanks, long term exposure to this condition can be stressful to the fish and should be used with caution, for limited periods of time, and by experienced hobbyists. 

When keeping corals in a saltwater aquarium, salinity range is less wide and very important. The salinity range that is required to keep healthy corals should be between 1.025-1.028. More importantly than choosing a target within this range, is stability and consistency. Healthy, colorful, thriving corals need and must have a stable salinity if you are going to be successful with coral husbandry.  

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