Where to Buy

AquaMaxx designed the REEFractometer specifically for reef aquarium use to measure the salinity of natural sea water (NSW). Additionally, the AquaMaxx REEFractometer is calibrated at a natural seawater temperature of 77°F. Most handheld saltwater refractometers available in the hobby are designed and calibrated for testing brine solution (ie. sodium chloride) at 70°F and does not account for the refractive index of natural sea water and the warmer reef temperatures. This is a very important distinction: other salinity refractometers used for marine aquariums are designed to test saltwater and nothing else! The AquaMaxx Reef-ractometer is designed to measure the salinity of NSW taking into account all the other elements that comprise salinity in the reef aquarium at the correct water temperature. The difference can amount to a 4-5% differential.

Even though the largest percentage of salt in the sea is sodium chloride, the presence of other significant ions such as magnesium and calcium in NSW results in a different refractive index to that of brine. A standard (brine) refractometer will therefore not give the correct salinity for NSW and a conversion factor must be applied.

For example, a 35 ppt (parts per thousand) solution of NSW has the same refractive index as a 36.5 ppt solution of brine. When using a brine refractometer, an aquarium hobbyist should therefore look for a reading of 36.5 ppt when trying to achieve a reading of 35 ppt for NSW.

Large, Easier to Read Scale

One of the other problems with most refractometers is the scale displayed normally reads from 0-100 ppt when we are really only interested in the region from 30-40 ppt. The AquaMaxx REEFractometer has therefore been specifically designed to read from 1.000-1.030 which gives you much better resolution of a normal 1.000-1.070 scale.

Easier to Calibrate

The AquaMaxx REEFractometer is also designed to be easy to calibrate. Calibration can be done with either a calibration solution, or simply RO/DI water. Adjustments are easily done with the included screw driver.


  • Protective Hardshell Case
  • Pipette
  • Soft Cloth
  • Calibration Screw Driver

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