Salinity while sometimes considered secondary and often taken for granted is crucial to the health of our aquarium inhabitants. 

Generally, the specific gravity of salt water is around 1.025 or 33 parts per thousands.  While fish can tolerate swings that are higher or lower, most corals and invertebrates are far more sensitive and can stress if exposed to drastic salinity changes.  This is the reason why it is so important to make sure that your tank’s salinity is stable and when doing water changes, the salinity of your new water matches the water in the tank. 

Some hobbyist test their salinity by using a swinging-arm hydrometer but the problem is that they are hard to read and unless they are kept very clean, the floating arm will most likely render an inaccurate reading.  Most hobbyist use a refractometer.  Light will refract differently based on the salinity of the water.  The problem with refractometers is that they are hard to read, only work in a well-lit environment and they need to be calibrated.  Another instrument used for measuring salinity is a digital refractometer.  It uses the same principle as the refractometer but it relies on a computer chip to do the reading for you. 

IceCap, the same company that brought you the Smart RODI water filtering system and the Gyre 3K flow pump among many others, has released the brand-new Salinity & Temperature Digital Pocket Tester. 

This is a very handy, small and easy to use pen that can measure salinity as well as temperature.  Just scoop water from your aquarium or water changing vat and the pen will give you an accurate reading of your water’s salinity in three different units…


  • Specific Gravity
  • Parts Per Thousand and
  • Practical Salinity Unit or PSU


In addition to that, the pocket tester can also provide you with an accurate reading of your water’s temperature which is great to double check that your current temperature probe is correctly calibrated. 

The IceCap Salinity & Temperature Digital Pocket Tester works by measuring the electrical conductivity of the water.  It does not require for you to look through a small lens or stay completely still until the swinging arm stops moving. 

Simply attach the included rubber cup to the pen. This cup makes scooping water convenient and protects the pen from electrical interference. Since the tester measures conductivity, it is best if the water sample is isolated.  Aquariums usually have pumps and heaters that may interfere with the reading if you place the tester right in your tank.

Turn the pen ON and then scoop a sample of your water.  Give it a few seconds until you hear a beep and your tank’s specific gravity will show in a nice backlit LCD display.  There is no need to guess if the color change happens between the lines or if the lens is too blurry to even read it. &a

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