Red Sea Seawater Refractometer

Price Match

Please fill out the price match form. You must include a valid URL so we can validate and accept the price. If we are un-able to match the price we will inform you of the best price we can offer. You will receive a notification via email within 12 hours. You can then simply add the product to your cart at the discount rate.

Tel: 0203 697 3750

Close

Ask a Question

The best way to contact us is by email as we respond promptly at all times. Our offices are open Mon-Fri 9 to 5, but if you are unable to get hold of us, just leave a voicemail message with an email address, and we will get back to you.

Tel: 0203 697 3750

 6 Reviews
£35.99 (found this item cheaper? We'll price match it!)

Red Sea’s Seawater Refractometer offers exceptional accuracy, for measuring the absolute salinity of seawater at a temperature of 25oC/77 0F Want more info?

Availability:      In Stock - Get it by Tuesday, Oct. 24

Availability:      In Stock - Get it by Tuesday, Oct. 24

This item is in stock.
Orders placed before 2pm where all items are 'In stock' will be dispatched the same day. Once this item has been dispatched you will be provided with full tracking details.

Delivery:   Economy Courier Delivery

This item will be dispatched via a 3-5 day courier serivce. You can also upgrade to next day delivery for as little as £2.00.

You will be able to upgrade your delivery service upon checkout.

International Shipping:    Available

This product is available for International Shipping.

See our International shipping rates

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:

- 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 25oC/77oF, the normal temperature range for reef aquariums (most standard refractometers are calibrated at 15oC/59oF ).
- Easier to read, higher resolution display, focussed to the relevant range for reef aquariums of up to 40ppt
- Includes Integrated Automatic Temperature Compensation (ATC) for accurate measurement at standard ambient temperature.
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

Review :: Red Sea Seawater Refractometer
Submited By: Marco Luccisano,  October 18, 2016, 8:28 pm
Collected By Trustpilot
  I am happy with this purchase and it works as intended , the only thing is, if I understood correctly that to have an exact reeding the temperature of the water needs to be at 25 degrees celsius otherwise the reading will be slightly off depending on the temperature of the water you are testing . It would be great if you can set the refractometer to the temperature of your aquarium instead of the standard 25 C  
Review :: Red Sea Seawater Refractometer
Submited By: Andrew Lonsdale,  March 8, 2016, 12:43 am
Collected By Charterhouse Aquatics
  Can be challenging to use at times, so we now recalibrate before every use and we are still learning. As stated in another review, temperature does appear to impact it. Beautiful instrument, great in the right hands.  
Review :: Red Sea Seawater Refractometer
Submited By: Marc Peers,  January 31, 2016, 12:28 am
Collected By Charterhouse Aquatics
  Great refractometer. Clear easy to read display, quick and good qaulity.  
Review :: Red Sea Seawater Refractometer
Submited By: Antony Damianos,  April 2, 2015, 2:44 pm
Collected By Charterhouse Aquatics
  This is a quality instrument and it feels well made. I have piece of mind that my measurements are accurateThat being said, it is extremely sensitive to temperature fluctuations and needs regular calibration, to the point now I calibrate it each time I use it.The pipette supplied is of really low quality and within a couple of weeks it has split and doesn't draw water. I know this is a cheap thing to replace but at the cost of the instrument, it shouldn't need to be!  
Review :: Red Sea Seawater Refractometer
Submited By: Dave Supple,  February 27, 2015, 8:45 am
Collected By Charterhouse Aquatics
  Fantastic refractometer. Very clear display and so much better to use than my old one  
Review :: Red Sea Seawater Refractometer
Submited By: Dave Supple,  January 26, 2015, 10:43 am
Collected By Charterhouse Aquatics
  I'm so pleased that I finally broke down and spent the money. This refractometer is vastly superior to my old one. The reading is very quick and so easy to read. A vastly superior device. A must for all marine aquarists.  

Free Shipping Over £50

Spend over £50 on your order and qualify for free shipping. Next day and timed services available.

Find out more

Pay by Finance

We offer flexible monthly finance options. Credit is subject to application and status.

Find out more

Reward Points

As a thank you, we run the Charterhouse Points scheme. Earn points on every order.

Find out more