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Hydrometers & Refractometers

A hydrometer or refractometer measures the specific gravity of water in a saltwater aquarium or reef tank to determine the tank’s salinity level.

How to use a hydrometer
A swing arm hydrometer offers basic salinity testing. Simply place tank water in the hydrometer and the arm will point to the salinity level. Reef salinity is typically between 1.024 and 1.026 specific gravity.

How to use a refractometer
A salinity refractometer is a more advanced way of measuring salt levels. Place a few drops of water under the plate, point the refractometer at a light source and look through the eyepiece. A shift in color will indicate the specific gravity. Be sure to use a seawater refractometer with automatic temperature compensation.

Refractometer vs hydrometer
We recommend a refractometer because hobby level hydrometers lack precision.

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