Frequently asked questions about common problems

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  1. 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 disease?
  2. My fish are sick …they are not eating / lethargic / respiring heavily/ have had losses / changed colour / inflammation / sores and lesions ?
  3. My fish has a swollen / bloated abdomen.. ?
  4. My fish are upside-down/ can’t swim
  5. My fish are changing colour
  6. My fish has fin rot …eroded, frayed or inflamed fins ?
  7. My fish has parasites / flukes / white-spot … ?
  8. My fish is covered in whitish cotton wool / fish fungus … ?
  9. My fish are gasping at the surface and “breathing” very heavily?
  10. My fish have ulcers, raised scales, areas of inflammation, and “popeye”

New set up … ?

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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My fish are sick … ?

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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My fish has a swollen / bloated abdomen… ?

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:

  1. 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.
  2. 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.
  3. 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
  4. Viral diseases: Much the same signs as bacterial infections but no cure
  5. 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.
  6.  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
  7. Could indicate intestinal parasites. Making wet mounts of faeces for microscopic examination may assist diagnosis.

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My fish are upside-down/ can’t swim

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 buoyancy.

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 edge” procedure.

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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My fish are changing colour

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 simply genetics.

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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My fish has ragged fins / fin rot … ?

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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My fish has parasites … ?

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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My fish are covered in cotton wool /fungus … ?

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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My fish are gasping…?

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 used.

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 situation

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My fish have ulcers, raised scales, areas of inflammation

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 thebacterial disease page for more details

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