Page 77 - Koi Net - On-Line Koi Magazine - Issue 75

THERMOMETERS Scientific or professional digital thermometers are a bit
more expensive, again, but not necessarily hugely so.
AND KOI PONDS They will probably come with a calibration certificate,
although this is only valid for typically 6 months or a
year and then the device needs to be sent to a
laboratory and pass calibration checks before it can
Anne Nonamust
South Hants Koi Club be issued with a new certificate.
So, you have purchased a very cheap digital
thermometer from ebay or Amazon for your pond – is it
TAKE A up to the job? For the most part we pond keepers are
As Koi keepers it is very helpful to have an idea of READING not too concerned if a thermometer is out by a small
how cold or warm our ponds are to ensure the correct amount, so there is a way to do a simple check. First
feeding regime. It’s also useful to know if the ABOUT A put the probe into melting ice, the thermometer should
temperature in winter is falling too low and some type read 0 degrees C. Then place the probe into boiling
of intervention is required, although that is a problem FOOT BELOW water, the thermometer should read 100 degrees C. If
we don’t see so much of these days. both these results are within 1 degree then it’s good
THE SURFACE enough for use in a Koi pond. If not, throw it away! It’s
Years ago, before the electronic and digital age the also a good idea to do this check even if you have
THE MERCURY only domestically available thermometers were either purchased a more expensive thermometer, even these
mercury or alcohol types. Both are still in widespread
may possibly be inaccurate.
TYPE IS use so we are all familiar with them. They consist of a
small glass bulb that contains the chosen fluid and the Don’t forget, the temperature at the surface of your
ACCURATE glass continues into a long thin tube attached to a pond may be a couple of degrees or so different to
THROUGHOUT graduated scale giving a direct temperature reading. that at the bottom. A good compromise is to take a
The higher ambient temperature the more the fluid reading about a foot below the surface.
ITS RANGE expands and the higher the associated reading will be.
Simple but effective.
0.0ºc 100.0ºc
The mercury type is accurate throughout its range.
However, mercury is very expensive so most
thermometers use alcohol, which is much cheaper.
Unfortunately, it is difficult to manufacture the purity of
the alcohol to the right quality and this often means
that this type is wildly inaccurate and/or has an
inconsistent expansion rate over the temperature
range that it is designed to cover.
Now on to the digital age, these thermometers can be
extremely accurate. You can buy a simple version of a
digital thermometer for just a couple of pounds, but
just how accurate are these cheap ones? The truthful
answer is, usually not very. You can purchase slightly
more expensive ones, for example, from the Koi dealers
that advertise within this magazine, these typically
claim to be accurate to within 1 degree (centigrade).
MELTING ICE BOILING WATER
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