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Salinity - Is It
Really Important?
Salinity or specific gravity (sg) are terms used to describe
the amount of salt that is in our water. Rivaled only by
temperature it is the most important parameter in our
tanks! In most ocean areas the salinity averages 1.026. In
our reef tanks we lower that a bit to help reduce stress
(remembering that stress is the biggest killer in this
hobby). A fish only tank can go as low as 1.020 but a tank
with any inverts (corals, snails, shrimp, clams etc.) need a
minimum of 1.023 to survive. I recommend running our reef
tanks at 1.024. Beware! A
reef
tank with an SG lower than 1.023 or higher than 1.026 can
have disastrous results!
There are several tools that measure salinity or specific
gravity. Recently I found customers with salt levels WAY
high & determined that either evaporation was not being
replaced daily or the tools used were out of calibration.
Be responsible & replace evaporation daily & make sure your
tools are operating correctly. Your livestock depends on
you…& your tools. The most commonly used are:
Hydrometer:
Glass floating hydrometer with thermometer:
Pros: Inexpensive
Cons: Water movement makes reading them
difficult - inaccurate
Plastic swing
arm hydrometer:
Pros: Inexpensive
Cons: Unless rinsed after each use with
freshwater the swing arms can
coat with hard to see mineral deposits resulting in higher
salinity than what it displays.Some
have also been found to be inaccurately calibrated from the
factory!
Refractometer:
The Best
Choice!
Pros: A little more expensive but a lot more
accurate. Can be calibrated to ensure its
reading
correctly. Does not rely on batteries or any power
source. IMO...worth the peace
of mind!
Cons: The additional cost
Digital Electronic (PinPoint) Salinity Meter:
Pros: Expensive in comparison to the hydrometer
but a lot more accurate & provides
a digital
readout at a glance. Can be calibrated to make sure
its functioning properly.
Cons: The additional purchase cost & relies on
batteries or power source.
Bottom line, no
matter what tool you use to measure salinity in your tank it
is critical that it's working correctly.
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