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Why are they important?
Unusual behaviour such as heavy
breathing, rubbing, flashing, lethargy is often taken as a sign
of parasite disease - yet the same behaviour can be due to water
quality problems, internal organ disease or many other
causes. Without a microscopic examination of both the skin
and gills it is simply impossible to tell the difference and any
treatment undertaken is based on nothing more than
guesswork! While simply taking a guess as to the cause and
treatment required may work it is just as likely to
make matters worse. So microscopy is a vital and basic step in
diagnosing and treating fish disease.
Buying a microscope
They come in a wide range of types
and prices, costing less than a hundred to several thousand
dollars - although fish keepers generally do not require an
expensive model. There is also a market for good
second-hand microscopes.
It really depends on what you want
to use it for. Most of the common parasites such as flukes,
white-spot and Trichodina can be easily identified with the
cheaper models, but a better quality model is required for
critical examinations of cell structures and some small
parasites. Generally speaking as prices increase you are paying
for better engineering, illumination and optics
Models for fish keepers
There are two basic styles of
microscope available. The cheaper monocular model
has a single viewing tube (as above) - which is fine for
occasional use. The binocular models enable you to view
with both eyes, giving a better field of view. If you want
to take photos or video - then you will really need a trinocular
model with a dedicated phototube.
Illumination
The better the lighting - the
clearer the image. Most of the cheap models have an
understage mirror which reflects light to illuminate the slide.
This can pose problems in dull conditions or lead to contortions
with table lamps to try and improve the illumination of the
specimen being studied. By far the best option is a fixed
or plug-in understage light system, which gives a consistent
amount of light. A basic plug-in system can be purchased for
under $75 and, in my opinion, is money well spent. More
expensive microscopes have built-in halogen lamps with brightness
control
Stage
The stage is the part of the
microscope where the slides are placed for viewing. As you
will appreciate, only a small part of the slide can be seen at
any time and the slide needs to be moved to see other parts.
Incidentally, the view that can be seen at any time is called the
field of view, which reduces at higher magnifications.
On the cheaper models the slide is
held by clips and has to be moved manually - but this cannot be
done smoothly and it is virtually impossible to return to a given
position on the slide.
All but the most basic of models
have a mechanical stage fitted with vernier screws that allows
you to move the slide smoothly and examine it in a methodical
pattern. Again, this usually adds less than $75 to the
basic cost and is invaluable when scanning the slide for
parasites.
There are different qualities of
mechanical stage- and some of the more robust stages can be quite
expensive.
Here are a couple of sites which
sell microscopes suitable for our purposes:
Sonlight Microscope
Microscope World
Also, check with school,
universities, hospitals, etc. Often, they have microscopes which
they are replacing and generally, the older models in good
condition will be excellent for our purposes.
A word about eBay. There are many
microscopes available at eBay, Buyer Beware. If you know about
microscopes and trust the seller, then you might find a good buy.
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