Red Sea’s Seawater Refractometer offers exceptional accuracy, for measuring the absolute salinity of seawater at a temperature of 25oC/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 15oC/59 0F rather than 25oC/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’s Seawater Refractometer include:


Red Sea’s Refractometer display

The PPT scale on Red Sea’s Seawater refractometer is calculated using an algorithm for seawater and therefore will give a reading of the Absolute Salinity of seawater.

The PPT scale on regular salinity refractometers are calculated using an algorithm for Brine. Using a Brine refractometer for Seawater will give an error of approximately 1.5ppt in the salinity reading.


About Salinity

Salinity is a general term describing the concentration of salt in water. However, solutions of different type of salts have different refractive indexes.

Brine is a solution of Sodium Chloride (table salt) that contains 2 chemical elements.

Seawater contains approximately 70 chemical elements that include Calcium, Magnesium, Potassium etc. in addition to the Sodium Chloride.

Seawater and Brine of the same salinity (i.e. the same weight of salt/liter) have different refractive indexes and will give different salinity readings if measured on the same refractometer.

Refraction & refractive index

All transparent materials such as liquids refract (distort) light.

All transparent materials refract light differently and have what is called a “refractive index” which means how much a particular material distorts light.

Different concentrations of the same liquid have different refractive indexes.

The scale of a refractometer is calculated by using a mathematical algorithm that relates the measured refraction to its concentration for a specific liquid.

 

Refractive index and temperature

The refractive index of liquids change with temperature and therefore has a major effect on measuring salinity with a refractometer.

The algorithm for defining the PPT (and S.G.) scale for a refractometer is calculated for a specific temperature.

PPT readings from refractometers that are not calibrated for reef aquariums (i.e. 25oC) need to be adjusted according to a conversion table to give the actual PPT at the aquarium temperature. This is often a cause for misinterpretation of refractometer readings.

For example, using a seawater refractometer calibrated at 20oC will give a PPT reading that is approximately 1-1.5ppt lower than the absolute salinity of the same water sample at the normal aquarium temperature of 25oC.

Therefore, Red Sea’s Seawater Refractometer calibrated at 25°C/77 0F directly reads the absolute salinity of seawater with no need for temperature compensation factor)

ATC – Automatic temperature compensation

Temperature is probably the biggest cause of wrong readings with a refractometer. Calibration and testing of water samples should be done after the refractometer and water sample have equalized at the correct temperature.

Automatic temperature compensation (ATC) compensates for a few degrees of difference between the ambient temperature and the calibrated temperature of the refractometer. Larger temperature variations will give an error of approximately 1.0ppt in the salinity reading.

ATC does not adjust the PPT reading of a refractometer to the temperature of the aquarium!



We are a local Australian seller, located in Sydney, Australia.

All our products are posted from Sydney, not overseas to ensure our customers
receive a fast and hassle free transaction.

We as a team work hard to ensure every customer is left with the positive feeling after purchasing from our shop.

I cannot emphasize enough how important your feedback is to us.

Therefore, we request that you leave an honest feedback & review.

If you have any questions or require further clarification, please send us an email and we will be more than happy to assist you.


- We accept Paypal, Bank Transfer or Cash on Pick up

- Payment must be made within 3 days of the purchase being made

- We Only Ship items within Australia. International Postage can be arranged. Buyer must contact before purchase.

- We only send items to the registered eBay address. Please edit your postal address before check out.

- Please allow up to 7 working days for items to be delivered via Australia post.

- All our products are of high quality.
  If you, unfortunately, receive a faulty item, please contact us, and send it back to us within 7 working days.
  We will arrange a replacement or a refund ASAP.

- We warrant our products against defects in materials and workmanship for your product.
  We will repair or replace its product if, due to defective  parts or workmanship,
  it does not perform as specified.
  In no event does  this warranty extend to instances where the product is damaged through uses
  for which it was not intended, misuse, mishandling, removal and/or re-installation, neglect, accident
  or tampering.
  In no event shall we’re liable for any indirect, incidental or consequential damages,
  or lost  profits arising out of or related to this product, or the performance or  breach thereof,
  even if we have been advised of the possibility thereof.
  We're a liability to the customer, if any, shall in no event exceed the total of the consumer’s purchase price.
  Any representations or promises inconsistent, or in addition to this warranty are unauthorized and
shall not be binding upon us.

Have any questions or issues with any of our products? Please contact us via eBay message prior to bidding.