Refractometers are essential tools for reef aquarists to monitor tank salinity. However, getting reliable readings requires proper use and maintenance of the instrument.
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Calibrating with Reference Solutions
To ensure a refractometer is measuring accurately, it must be calibrated regularly using a reference solution. For saltwater tanks, a 35ppt solution is recommended. Add a few drops and adjust the screw until the interface lines up precisely.

Let the solution sit 1 minute before calibrating to equalize temperature. Rinse with RO water afterwards to prevent residue affecting future tests.

Sample Testing Technique
Rest samples on the prism for 1 minute before measuring to equalize temperature. Avoid bubbles by applying sample thinly and closing the cover smoothly.

Read at the bottom interface between blue and white fields for highest precision. A digital refractometerauto-measures for convenience.

Maintenance for Longevity
Rinse with RO water after each test to prevent residue influencing future results.

Regularly wipe down the prism with a soft cloth to remove fingerprints or debris that could disturb readings over time.

Store in the protective case when not in use to safeguard from scratches and ensure reliable service for many reefing seasons to come.