How to Monitor Salt in a Saltwater Aquarium

Salinity is the measure of the amount of solids dissolved in seawater, the vast majority of which are salts. Salinity is most accurately measured by using a salinity refractometer. The salinity refractometer is a scientific instrument that provides highly accurate and rapid salinity determinations. Many salinity refractometers have been manufactured with automatic temperature compensation. This feature eliminates the need for temperature compensation charts. Salinity refractometers are easily read by the aquarist.

Things You'll Need

  • Marine aquarium
  • Refractometer
  • Distilled water
  • Pipette
  • Soft cloth
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Instructions

    • 1

      Calibrate the refractometer before use. Hold the refractometer in a horizontal plane and carefully flip open the refractometer's glass or plastic daylight plate. Use a pipette to place two drops of distilled water onto the prism. Close the daylight plate and gently press it down to spread the water across the entire surface of the prism.

    • 2

      Point the front of the refractometer toward a strong, preferably natural, light source and look into the eyepiece. Check to see that the line created by light passing through the distilled water falls at the zero point of the index.

    • 3

      Use the screwdriver supplied with your refractometer to adjust the calibration screw on the refractometer until the line falls at the zero point of the index.

    • 4

      Flip up the glass or plastic daylight plate that covers the prism.

    • 5

      Draw up three or four drops of distilled water in a pipette and rinse the prism, by dripping the distilled water onto it. Gently dry the glass prism with a soft cloth.

    • 6

      Flush out the pipette, by drawing up and releasing water from the aquarium three or four times.

    • 7

      Fold back the glass or plastic daylight plate. Draw up water from the aquarium and place one drop on the prism. Very gently push down on this plate, in order to spread the water sample across the entire surface of the prism.

    • 8

      Point the refractometer toward a strong light source and place the eye piece against your eye. A natural light source is always best.

    • 9

      Focus the refractometer as required, by gently turning the focus ring that is positioned in front of the eye piece.

    • 10

      Read the point on the index at which the line falls to determine the salinity of your aquarium water.