New set up ... I
have recently started a new pond or tank and introduced several
fish. I have lost several fish. There are no marks or signs of
My fish are sick
...they are not eating / lethargic / respiring heavily/ have had
losses / changed colour / inflammation / sores and lesions ?
My fish has a
swollen / bloated abdomen.. ?
My fish are
upside-down/ can't swim
My fish are changing
My fish has fin rot
...eroded, frayed or inflamed fins ?
My fish has
parasites / flukes / white-spot ... ?
My fish is covered in
whitish cotton wool / fish fungus ... ?
My fish are gasping
at the surface and "breathing" very heavily?
My fish have ulcers,
raised scales, areas of inflammation, and "popeye"
This is caused by new pond/tank syndrome due to a build up of toxins
such as ammonia and/or nitrite. It takes a new filter at least 6-8
weeks to mature - that is for the nitrifying bacteria to start to
colonize the filter media. Ammonia is freely excreted by fish as part of
normal metabolism and during this maturation time the levels of these
toxins can rapidly build up to dangerous levels. It is important to only
introduce only few fish at a time during this period, and
constantly monitor (at least twice weekly) water quality for ammonia, pH
and nitrite. For more details see the nitrification page. If levels do
rise they should be reduced by carrying out a 10 -50% water change
(depending on the degree of pollution). For example, if the ammonia is
twice the acceptable level, a 50% water change will only reduce it back
to an acceptable level, whereas a 25% water change would still leave it
1½ times the acceptable level! Obviously, smaller more frequent
water changes are better. As conditions improve the frequency of testing
and water changing will slowly reduce. Once levels have stabilized only
introduce a few new fish at a time as every new addition will increase
the ammonia load on the filter.
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It is possible to make a guess - but most guesses are usually
wrong. Unfortunately fish disease, as with any other animal
pathology, is a complex subject and unfortunately it simply isn't
possible to make a full and accurate diagnosis without examining the
both affected fish and the water they live in. The vast majority of
problems can be diagnosed fairly easily by testing a range of water
parameters and carrying out a thorough examination of one or two fish.
It is important to bear in mind that we need to establish what disease
is present and any underlying causes. This type of methodical
examination is described in detail on the fish health work-up pages.
However, this does presume that the fish keeper has both the necessary
basic equipment and skills to carry out the examination. If not,
then it is important to try and get professional help, either from a
fish-friendly vet or an aquatic specialist who will carry out the
examination for you. The only alternative to a proper diagnosis is
"dartboard" medication in which the water is treated with a
succession of different chemicals in the hope that one will work.
But such an approach usually makes matters worse.
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This is a common but difficult problem and typifies the problems
involved in fish disease diagnosis. Abdominal swelling is not a disease
- but a clinical sign of several possible health problems. Because
an internal disorder is involved, in most cases it isn't possible to say
what the problem was until a post mortem is carried out. The most
common causes are:
A genetic disorder that usually shows
as the fish grows older. In the early stages this seems to
cause little discomfort for the fish and it will lead a normal life
for some time - often several years.
A tumour or growth. The only
option in this situation is surgery, which clearly requires
professional help. However, the survival rate of such procedures is
very low as this is still very much an experimental procedure.
Systemic bacterial infection, which is
usually accompanied by raised scales, protruding eyeballs and
sometimes reddening / inflammation on the body. If caught
early enough this may respond to a course of antibiotic injections.
Bath treatments are rarely successful See bacterial infections
Viral diseases: Much the same signs as
bacterial infections but no cure
Internal organ disease - such as heart
problems- leading to an accumulation of fluid in the abdominal
cavity. This leads to a balloon-shaped swelling and the abdomen
feels very soft and sqidgy - unlike a tumour which tends to feel
hard. No cures, and heart transplants are just not on.
Intestinal blockage /
constipation: This is more usually associated with loss of
equilibrium, but in some severe cases it can lead to swelling. The
only possible treatment is either try to feed the fish a few frozen
peas, which act as a laxative, or else try baths in Epsom
salts (70g / litre for 5 minutes) which has the same effect. If the
condition is advanced, the success rate is likely to be poor
Could indicate intestinal parasites.
Making wet mounts of faeces for microscopic examination may assist
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This is a common problem whereby fish lose their equilibrium and are
unable to maintain their position. This can result in the fish
swimming awkwardly, laying upside-down either on the bottom or top of
the water, or unable to maintain a horizontal position in the
water. This is often attributed to swim-bladder problems and
indeed this is the most common cause of loss of equilibrium. The
swim-bladder is an air-filled sac laying just under the backbone at the
top of the abdominal cavity. By inflating / deflating the swim-bladder,
the fish can adjust its position in the water and maintain neutral
The swim-bladder can be affected by bacterial or viral diseases. In
addition the swim-bladder may malfunction, leading to over or under
inflation. Clearly anything which affects the proper functioning of the
swim-bladder will also affect the fish's equilibrium.
However, before diagnosing all equilibrium problems as swim-bladder
disease, we should be aware that there are other conditions which can
cause buoyancy problems. Disease in other organs such as kidneys
and intestines for example can also cause problems. This can
happen if there is any swelling of the affected organs leading to either
a change in organ density or pressure being put on the
swim-bladder. This is often a problem with fancy goldfish whose
abdominal cavity is tightly packed.
Treatment is difficult, mainly because it is virtually impossible to
diagnose the cause and secondly there are only a few conditions that
will respond to treatment. It is always worth considering a course
of antibiotic injections in case a bacterial infection is involved. An
attempt should be made to see whether the fish is defecating, in case
the problem is being caused by an intestinal blockage. If this is
suspected it is worth either trying to feed the fish a few frozen peas,
which act as a laxative, or else try baths in Epsom salts (70g /
litre for 5 minutes) which has the same effect.
If these treatments do not work, there is little else that can be
done. There is some work being carried out on exploratory surgery, but
there are very few veterinarians undertaking this "cutting
There are a few reports of fish recovering from balance problems, so
it is worth giving the fish some time. One report suggested
"wedging" the fish upright between two objects was
helpful. If there is no sign of recovery after 7-10 days, the
kindest thing is to euthanase the fish.
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A fairly common situation arises when fish literally change colour,
either all over or just parts of the body. The most common
situation is when previously coloured fish turn white. Fish skin
colouring is a complex subject. Fish skin contains different types
of pigment cells or chromatophores, which are under the control of the
hormonal and nervous systems.
Fish which are diseased often change colour, but this is usually a
fading/darkening/dulling of the skin rather than an actual colour
change. There are a few conditions in which there is a colour
change but these are rare.
The most common causes are either nutritional deficiencies, so one
could try a change of diet, water chemistry such as pH or hardness, or
In virtually all cases the fish appear perfectly healthy apart from
the colour change and eat and swim normally. So apart from perhaps
changing the diet and checking water parameters there is nothing that
can be done to reverse the colour change.
As a thought, it might be a little upsetting if your goldfish becomes
a whitefish, but pity the koi owner who has paid several hundred pounds
(or dollars) because of the fish's perfect colours / pattern, simply to
watch the colour and patterns disappear!!!!
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Fin rot is nearly always a sign of stress and the most important step
is to try and determine why the fish is stressed and resolve the
problem. It is important to realise that the stress could be
initiated by virtually anything, for example poor water quality,
parasites, etc. - so therefore it really needs a full examination of
both the fish and the water as described in the fish health work-up. If the problem is
caught early enough, simply removing the source of the stress will be
enough and the fish will probably recover. However, if the problem
is more severe and the infection has a firm hold it may be necessary to
trim away the diseased portion of fin and consider a course of
antibiotics. Obviously this may require professional
assistance. For further details see the fin rot page.
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If parasites are suspected, a skin and gill scrape are essential.
This will show for certain if parasites are present; what species they
are and how many. In turn these findings will influence the best
treatment plan. Certain treatments seem to work better than others
against certain parasites - so knowing what you are dealing with
gives you a better chance of success. A follow up examination at
the completion of the treatment course is important to ensure that it
has been effective. It should be remembered that fish will react to poor
water quality in the same way, so all water parameters should be checked
before any treatments are used. See parasites
for more details
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Fungus is nearly always a secondary infection, so it is important to
find out the underlying cause, which could be water quality, parasites
or a bacterial infection. Obviously these need to be resolved at the
same time as treating the fungus. If the affected area is fairly
small a combination of topical treatment and a long-term bath in
malachite green or some other anti-fungal treatment should be
successful. However, if the affected are is large, the outlook is poor.
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This is a sign of respiratory problems. The most common cause is some
form of gill disease, but internal disorders such as heart disease can
also cause respiratory problems. It is important to establish the
cause and resolve any underlying problems before any treatments are
First check ammonia, nitrite and pH as unacceptable levels can cause
gill damage. Check dissolved oxygen levels (cheap kits are readily
available). The affected fish should be examined for signs of gill
parasites and gill disease. This obviously requires a level of
skill and experience and access to a microscope. Professional assistance
should be sought if necessary. Treatment depends on the cause of
the problem. See gill disease page
for more details. Any suspicion of gill disease must be taken seriously
and an accurate diagnosis made as the wrong treatment can exacerbate the
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These are usually typical signs of a bacterial infection. Depending
on the severity of the problem, the treatment can range from
antibacterial bath treatments, to topical treatments or antibiotics. As
with virtually all fish disease it is important to make a full
examination of both the fish and water to determine if there are any
underlying or secondary problems. These must be resolved at the
same time as treating the infection.
If, after providing the best possible conditions, there are not clear
signs of recovery within 5-7 days, then a revised treatment plan should
be introduced. If, for example, a proprietary treatment had been
used and there was no improvement, the next stage would be topical
treatments combined with an appropriate antibiotic. It is usually
advisably to take a swab sample from the lesion and have this cultured
and checked for antibiotic sensitivity so that you know the best
treatment. Your local vet should be able to arrange this. Obviously,
unless you have some experience and skill, you may need professional
help for these procedures. See the
bacterial disease page for more details
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