Red Sea Seawater Refractometer offers exceptional accuracy, for measuring the absolute salinity of seawater at a temperature of 25^oC/77 ⁰F.

Most refractometers used within the aquarium hobby are not specifically designed for reef aquariums and use an algorithm for the measurement of brine (NaCl rather than seawater) and at a temperature of 15^oC/59 ⁰F rather than 25^oC/77?⁰F. Thus, a measurement deviation of up to 1.5ppt is possible, which can have a significant adverse effect on coral growth and coloration.

 Main features of Red Sea Seawater Refractometer include:

• Directly reads the absolute salinity of seawater at 25^°C/77 ⁰F  ( No need for seawater or temperature compensation factors)
• Specifically designed for the ionic content of seawater (NSW) for more accurate salinity measurement (industry standard refractometers are calibrated for salt brine ).
• Calibrated for seawater (NSW) at 25^oC/77^oF, the normal temperature range for reef aquariums
  (most standard refractometers are calibrated at 15^oC/59^oF ).
• Easier to read, higher resolution display, focused to the relevant range for reef aquariums of up to 40 ppt
• Includes Integrated Automatic  Temperature Compensation (ATC) for accurate measurement at standard ambient temperature.

High Accuracy Seawater Refractometer

How to Use

Let the refractometer and the water sample come to the same room temperature first — a sample straight out of a 26 °C tank read on a cold instrument is the most common source of error.

1. Hold the refractometer horizontally and open the flap.
2. Using the pipette, place a few drops of the sample on the glass prism. Do not dip the refractometer into the tank.
3. Close the flap so the sample spreads without air bubbles, hold it up to a light source and read the boundary line against the scale.

Rinse the prism with RO water and dry it gently after every reading. Salt left to dry on the prism is what puts an instrument out of calibration.

What’s in the Box

Refractometer with integrated automatic temperature compensation, sample pipette, calibration screwdriver and a protective case.

Calibration & Care

Calibrate with RO or distilled water at room temperature: place a few drops on the prism and use the screwdriver to bring the boundary line to zero. Check it monthly, and always after a knock or a temperature change.

This instrument reads the absolute salinity of sea water directly at 25 °C, on a scale focused to the reef range up to 40 ppt. Most aquarium refractometers are calibrated for sodium chloride brine at 15 °C instead, which can put a reading out by as much as 1.5 ppt — enough to matter for coral growth and colour.

Freshness & Storage

Every batch we dispatch carries a minimum of 6 months’ remaining shelf life. Store this product in a cool, dry place away from direct sunlight, with the cap or inner foil closed tightly after each use.

Returns & Replacement

Returns are accepted within 7 days of delivery, provided the item is unused and in its original packaging. Manufacturer-sealed items cannot be returned once the seal is broken, and sale-priced items are not refundable.

If your item arrives defective or damaged, message us on WhatsApp with your order number, or email us if you would rather, and we will replace it. Approved replacements are delivered within 3 to 5 business days. Transit damage is covered by insurance on every shipment. If tracking shows delivered but nothing reached you, tell us within 72 hours, which is the reporting window Indian couriers allow. Damage caused during installation or use is not covered; replacement spares for such cases are chargeable.

Full terms are on our Cancellation & Returns page.