Koi Skin Scrapes: A How-To Guide

Published on May 1, 2014

Skin scrapes are vital to accurately diagnose fish parasites. This photo illustrates the proper technique for performing a skin scrape.
Skin scrapes are vital to accurately diagnose fish parasites. This photo illustrates the proper technique for performing a skin scrape.

If your koi are behaving oddly,
you’ll need to determine the reason for
the strange conduct in order to resolve
the issue that has occurred. First, analyze
pond or tank water with a test kit to
determine if all water parameters are
within acceptable levels. Simple tests can
rule out water quality as the trigger for
unusual koi behavior and point you in a
different direction. If water quality passes
with flying colors, then proceed to parasite
activity as the next possible cause.

## Fish Parasites ##

Fish parasites are both microscopic
and macroscopic. Skin scrapes must be
performed to identify microscopic parasites,
as this type cannot be seen with
the naked eye. Fish parasites are usually
discovered this way; the majority of
harmful koi parasites are microscopic.
(Fish are like dogs and cats in that if you
don’t actively prevent parasites, you will
end up treating for parasites.)
kloubec_slide1

The purpose of taking a skin scrape is
to obtain a sample of mucus from a koi’s
cuticle, or slime coat, for analysis under
a microscope. The mucus specimen is
examined for significant parasitic existence.

Remember that parasites are always
present in low numbers, but when a koi
has been stressed the parasites will flourish
and can become problematic.

Typical koi behavior suggesting that
skin scrapes should be performed:

■ Flashing and darting, or rubbing on
pond edges, as if to rid an irritant

■ Loss of appetite and general
sluggishness

■ Hanging motionless in water

■ Unusual gill activity; clamped gills
or excessive movement or panting

■ Clamped fins

■ Isolation; not mixing with other koi

■ A foggy eye, patches of fungus,
bumps, sores, ulcers or lesions on the
body or fins

■ Congregating in high oxygen
concentration areas such as waterfalls or
around air stones

■ Lying on its side on pond bottom,
exhibiting sharp movements if disturbed
only to resume lying-down position

■ Reddening of skin or fins
Performing skins
scrapes can be a daunting
task. Getting
good quality skin
scrapes will take practice.
Accurate parasite
identification with a
microscope will take
even more practice.
With time, you’ll gain
confidence in handling
your koi and become
proficient at obtaining
and preparing specimens
for microscopic
examination or biopsy.

## Prep Work ##

Things you will
need to perform
successful skin scrapes:

■ Sock net

■ Koi viewing bowl

■ Sterile glass slides

■ Sterile plastic cover slips

■ Microscope

■ Pen and paper

■ One cup of pond water

■ Eye-dropper

■ Tweezers

■ Hand towel

■ A helper

Assemble all necessary equipment for proper and successful skin scrapes or gill biopsy before netting your koi.
Assemble all necessary equipment for proper and successful skin scrapes or gill biopsy before netting your koi.

Assemble all of the necessary equipment
on a clean, dry surface. Before you
begin, decide how many scrapes you will
be performing. Set out a clean piece of
paper for every scrape, and label and
number each one with a corresponding
scrape location: left flank, flank to
tail, right gill, et cetera. These sheets of
paper will keep your slides organized
and provide a great place to jot down
notes both during sample collection and
during examination with a microscope.

See the sidebar for a list of suggested
skin scrape sites. Once you’ve made these
preparations and have chosen your sites,
you’re ready to begin!

## Performing Skin Scrapes ##
Fill a koi viewing bowl with water
from the tank or pond just to a depth
sufficient to cover the fish. Using a
sock net, carefully put one koi into the
viewing bowl. You will be holding the
fish with one hand and performing the
skin scrape with the other. Try not to
touch the areas designated as scrape
sites. Never blot, wipe or wrap the koi
in a towel. This would remove the pests
that you are trying to capture from the
cuticle.

When handling koi you should try
to remain calm and maintain quiet
surroundings. If the koi is of substantial
size, a helper may be needed. It is a
good idea to give your koi a break and
a chance to breathe in between each
scrape. By releasing it momentarily,
you’ll ensure it gets through the ordeal
with minimal stress.

Start by holding your fish against the
side of the viewing bowl with its flank
(side) out of the water. Grasping the
slide firmly, hold it at a 45-degree angle
and press it down on the fish. Apply
some pressure and drag the edge of the
slide along the flank, from the shoulder
toward the tail. Never go against the
scales, as damage may occur. By applying
slight pressure you should be able to
scrape some mucus from the skin. You
only need a small amount; about the size
of a pencil eraser. The intended prize,
mucus, will be clear or vaguely opaque.

Once you have a
sample on the slide,
place one drop of
pond water on top
of the mucus and
gently place a cover
slip on top of the
mixture. The cover
slip will force the
mucus to spread out
on the slide, perfect
for viewing under a
microscope. Place
your prepared slide
on the appropriately
labeled paper and
keep it out of direct
sunlight. Now, move
on to gather more
samples.

Obtaining a sample of gill tissue is challenging but crucial for properly diagnosing gill parasites and/or gill disease.
Obtaining a sample of gill tissue is challenging but crucial for properly diagnosing gill parasites and/or gill disease.

For best results,
your samples should
be examined within
30 to 60 minutes of being collected.
Tweezers will come in handy if any
macroscopic parasites are discovered,
such as anchor worm or fish lice.

## Gill Biopsy ##
Taking a sample from the gill of
your koi is a little trickier. Fish really do
not like to cooperate with whomever is
lifting their gill plate cover (operculum)
or sticking an object under it. You will
most likely need a second set of hands to
help when taking gill samples.

Now is your chance to get a good look
at the gills and visually inspect them for
damage or signs of tissue malfunction.

You should take note of
anything unusual, such
as pale pink streaks or
areas of discoloration
within the normally
crimson red gill tissue.
White edges, frayed
tips, holes, heavy mucus
or blood clots on the
gill filaments are also
reasons for concern.
Also, any buildup of
scar tissue resulting in a
trunk-like appearance of
the individual delicate
gill tissues is an indication
of heavy parasite
infestation. All of these
conditions are evidence
of gill damage from
parasite activity or may
also be an indication of
chemical burn.

Instead of obtaining
a mucus sample with
the edge of a glass slide,
this time you will use
a sterile plastic cover
slip to retrieve the gill
sample.

## Performing Gill Scrapes ##

Again, hold your fish
against the side of the
viewing bowl. Working
quickly, lift the operculum
and gently wipe
the gill filament with a
corner of the cover slip,
then release the fish.
This sample will look
different than a body
skin scrape. It will be
pink or red and look
like tissue rather than
clear mucus. Don’t be alarmed if you get a little bit of blood with the sample or
if the fish bleeds from the gill following
the procedure. Place the cover slip,
sample side down, on a clean glass slide.
To stay organized, set the slide down
on your previously numbered sheet of
paper. Now you can study the scrapes
under a microscope and review your
notes, or continue taking more samples.

## Happy, Healthy Fish ##

Performing a skin biopsy or skin
scrape can be intimidating, and getting
good quality scrapes will take practice
and patience. But if your koi are not
their usual, lively selves, getting quality skin scrapes — and learning to analyze
them — is the first step in restoring
them to health! The sooner you accurately
diagnose the existence and type
of parasites that may be plaguing your
koi, the sooner your fish will be bright,
active, happy and healthy again.

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