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AquaMaxx REEFractometer Refractometer


Item #: UJ94644

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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

Manufacturer information

AquaMaxx is a Southern California-based aquarium supply company that entered the market in mid-2008 with a line of affordable metal halide bulbs. The brand quickly gained recognition as word spread about the high quality and low cost of their lamps. In 2009, AquaMaxx released a line of aquarium filter socks and, in early 2010, unveiled an assortment of high-performance protein skimmer accessories and upgrades.

5 Stars


Reviewed on
March 10, 2021

No, I would not recommend this.


Pros: nothing

Cons: Inaccurate readings.

I bought this a few years ago. Adjusted to zero per instructions and adjusted salinity to 35 PSU over the course of a couple weeks. Held it there while corals gradually all died. Had my water tested by ATI. Before sending in the water I tested the water with this refractometer and it read 36 PSU. Got ATI test results today and test showed 24.6 PSU. I checked again today and this device still shows tank water is at 37 PSU. My water salinity is very low solely because of this device. When I tested with RODI water it shows 0. When I adjust the device to show the true salinity, RODI test sample reads less than zero. This device is junk and cost me all corals.

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Reviewed on
July 08, 2020

Yes, I would recommend this.

Easy to read

Easy to read. Seems accurate and reliable.

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Reviewed on
July 12, 2017

Yes, I would recommend this.

Excellent Refractometer!!!

Pros: Large read scale from 1.0-1.030SG, rugged aluminium body, easy to calibrate with RO/DI water, adjustable focus eye piece, hard storage case.

Cons: I regret I didn't get one sooner.

I have been using this refractometer for a month now and all my corals seems to be a lot more happier than before. I suspect that my previous measurement from my old refractometer was off by about 0.02 higher which was at 1.028. It's time for a salinity check in the tank before a water change and I'm so glad I got the Aquamaxx Aquariums refractometer. The larger scale from 1.0-1.030sg made it so much easier to read vs the typical 1.0-1.070sg scale that most refractometers are sold with and it is that much more accurate as well. Holding in hand the unit is extremely rugged built with aluminum body and adjustable focus eye piece. I calibrated the refractometer with 0TDS RO/DI water and my water was shown 1.026 dead on. I'm glad to see the corals are going a lot better and the larger read scale made it so much easier on the eye for me. I hightly recommned this product over the cheaper generic ones.

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