How to Read a Hydrometer for Salt Water Fish

If you own a saltwater fish tank you must have a hydrometer to test your water salinity. Taking accurate water salinity readings are essential to maintain the health of any marine aquarium. Many specific types of fish and corals demand specific salinity levels, or else they may suffer from diseases or possibly even die. Although there are many different brands of hydrometers on the market today, most all are read exactly the same way.

Things You'll Need

  • Hydrometer
  • Saltwater aquarium
  • Flat surface
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Instructions

    • 1

      Rinse your hydrometer out with tap water.

    • 2

      Dip the hydrometer into the aquarium and fill with water from approximately 6 inches beneath the surface.

    • 3

      Pour out excess water until it reaches the fill-to line on your hydrometer.

    • 4

      Tap the hydrometer once gently on a flat surface to remove air bubbles from inside.

    • 5

      Place the hydrometer on a flat surface and wait five seconds.

    • 6

      Read the hydrometer by looking at where the "arm" or "needle" stops in the number range.