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Diseases of Goldfish

Brief Description

Goldfish are known to be highly susceptible to various diseases because of all the selective breeding that takes place. Common and comet goldfish are the hardier variations of all the goldfish varieties available in the aquarium industry. The fancier, more selectively bred varieties of goldfish are more apt to contracting the various diseases that can ail goldfish. Books and internet websites on fish diseases can be your best source of information to finding out all about goldfish diseases thus it is highly recommended to have access to either or both of these sources of information when owning goldfish, especially the fancy varieties of goldfish.


Disease prevention is the best solution to any type of fish disease. Although prevention does not always work 100% of the time it definitely improves the odds of having healthier goldfish.

  • The first step in disease prevention is choosing only the highest quality fish for purchase. When looking to purchase a new goldfish approach the task with high standards in mind. If the aquarium retail store has dirty fish tanks that contain unhealthy and unhappy looking fish, chances are your fish will not survive for very long. If the stores tanks appear to be in good, clean, healthy conditions and contain fish that appear robust and hearty, chances are your fish will continue to thrive as long as it is well taken cared of once you have purchased it.
  • The second step to disease prevention is keeping the aquarium water at optimal quality. Goldfish have the tendency to produce a lot of waste and yet are fairly sensitive to unclean water. When keeping goldfish it is highly advisable to provide good water filtration and to perform plenty of partial water changes. Be careful not to over feed them because goldfish have short digestive tracts and no stomachs which mean they absorb less of the foods they eat and excrete most of it as fecal matter back into the water. The increased levels of waste cause higher levels of ammonia to buildup in the water over shorter periods of time which can lead to many different health problems. By changing the water often and keeping it well filtered most health problems can be prevented.
  • Adding a little bit of aquarium salt to the fish tank may help to prevent some of the diseases that goldfish are prone to. Ich and fungus are unlikely to develop even if small traces of saline are detectable in the aquarium water. The key is to keep only minimal amounts of aquarium salt in the tank water so that you can add more if it is needed in the event of an outbreak of some sort. Definitely be cautious not to add to much salt to the water because goldfish are not marine animals and can only handle slight amounts of salinity.

Medication and Chemicals:

Medication and chemicals should definitely not be used as a prevention method of dealing with diseases for goldfish or any other fish. It is very important to consider limiting the use of medications in the aquarium. Using medicine only when it is absolutely necessary will increase its chances of working properly when it is actually needed. If medications are constantly present in the aquarium different strains of certain diseases are likely to develop; strains of disease that become resistant to the medications causing medicine to become ineffective. As each goldfish disease is listed below, the proper medications and treatments will be mentioned.

What not to do:

Once you know the common diseases and conditions a goldfish can suffer you should be able to provide better care for your own goldfish. However there are several things that aquarists often forget when dealing with sick fish. So here is a short list of things to remember not to do.

  • Do not add additional fish to the aquarium until your fish are free and clear of disease and stress. Do not over crowd the aquarium because that will cause a whole mess of problems. Stress levels, waste levels, chemical levels such as ammonia, nitrite and nitrate will rise.
  • Do not use multiple medications unless it specifically says it is safe to use in conjunction with one another, usually different medications of the same brand will allow to simultaneously use two different medications.
  • Do not perform too many complete water changes or move your fish around unless it involves moving the sick fish to the hospital tank. Disturbing the tank too much will cause more stress to the fish which will then cause the fish to not be able to heal from their present ailments. As much as possible try to do partial water changes as you would normally do to keep the water conditions up to standard.

Disease/Conditions and Treatments:

  • Ich

    Ich or ick is short for Ichthyophthirius multifilis, which is one of the most common diseases among most fish. This is a disease that appears as white spots that look like grains of salt on the skin and gills. Usually brought on when the fish is experiencing a lot of stress or when new fish are introduced into the aquarium. The first thing to try is raising the temperature and adding saline to the aquarium water. Be aware of the type of fish you have because not all fish can handle salt in the water. Loaches, corys, snails and some aquatic plants are especially sensitive to it and may die if there is too much salt in the water. If that does not work you can try using medications that contain copper.

  • Fungus

    Fungus can often form at the site of wounds or sores like an infection. The fungus will appear like a little ball of cotton at the edge of the open wound and it is caused by bacteria. There is an antibiotic called Maracyn that treats bacterial infections to help get rid of fungus.

  • Swim bladder disorder

    Swim bladder disorder is common among fancy goldfish with shorter, rounder bodies. This is because their swim bladders are developed differently due to their compromised shapes. Goldfish are selectively bred to create the round shaped bodies and high hunched backs so the shape and position of each of their organs are not always as it should be. The swim bladder is an organ that maintains a fish’s equilibrium allowing it to swim normally. If that swim bladder is not functioning properly it can cause high stress to the fish and eventually lead to death. Doing a complete water change could be the best solution because studies show that a nitrate-free environment can cure swim bladder disorder.

  • Gasping at the surface

    Gasping at the surface or laboured breathing, the fish is not getting enough oxygen. High temperatures, saline, and elevated chemical or medicine levels can cause the oxygen levels to go down. This one condition where these treatments are not recommended. Check to see that your filtration system is working properly. Also check to make sure there are not any oils or scum on the surface of the water. Gas exchange at the water’s surface is how the fish get their oxygen so make sure there is a certain amount of agitation at the water’s surface. If there is any amount of oil or scum preventing the water from absorbing the oxygen it should be taken care of it right away. Scoop water from the top of the waters surface until it seems like the gunk is gone. It is very important to have plenty of surface area with sufficient agitation or water movement where oxygen can enter the water.

  • Constipation

    Constipation is common and easy to solve problem for goldfish. Goldfish do not have stomachs to hold onto their meals for the digestion process. All they have are short digestive tracts through which their food quickly passes. It is important for their proper nutrition that their foods are quickly digestible and easy to pass which is why special foods are made for goldfish; to absorb as much nutrients as possible over a short amount of time. When a goldfish becomes constipated it could cause other problems such as swim bladder disorder so it is important to solve the problem right away. You may notice your goldfish looking lethargic and swollen which are clear signs of constipation. Stop feeding your goldfish his normal flake or pellet foods for a few days and start giving him some veggies. Just like humans, fish can benefit from well balanced diets. Spinach, peas or lettuce leaves can be fed to your goldfish if you cook them until they are soft enough for the fish to digest. When you go back to feeding flakes and pellets to your goldfish it would help to first soak the food in water to soften it for ease of digestion.

  • Fin and tail rot

    Fin and tail rot are symptoms of stress due to poor water conditions, over crowded tank, or rough treatment by humans or other fish. It is a very easy to recognize condition where the fins and tail of the goldfish become shredded or they rot away. Fin and tail rot is caused by several types of bacteria in the water. The first course of action to take is to do a partial water change and then add antibiotics such as Maracyn 2. This should get rid of the bacteria that cause the fin and tail rot condition, but to treat the damaged goldfish fins there is a medication called Melafix that aquarists use to treat wounds and repair fin damage.

  • Pop eye

    Pop eye is a condition, not quite a disease that is characterized by the eyeball popping out of the eye socket. It can have several different causes: water of poor quality, infection from bacteria, or inflicted injury from other fish. Pop eye is the result of swelling and retaining fluid behind the eye area causing it to bulge. The first form of treatment for Pop eye is to separate the sick goldfish into a hospital tank with very clean water and well aerated water with no activated carbon filter. Sometimes just that can help to reduce the swelling and infection in the eye, but if it does not then treat with Tetracycline which is a full range of medications that treat bacterial infections.

  • Dropsy

    Dropsy is a disease that presents symptoms such as swelling of the abdomen which then causes the scales of the fish to stick out from the body. These symptoms are caused by the buildup of fluids in the fish’s abdominal area and the goldfish will become lethargic and uninterested in food. Bacteria or contaminated food could very well be the cause of this disease which means that it can be treated through the use of a broad spectrum antibiotic. If the cause of the Dropsy is neither contaminated food nor bacteria it could be due to kidney, liver or heart failure, in which case it cannot be treated with any medications.

  • Hole in the head disease

    Hole in the head disease affects goldfish as well as all other freshwater fish. It is not known for sure what causes this disease but there is speculation that it could be caused by bacteria, parasites, nutrient deficiency, or poor water quality. This is a progressive disease in that it takes some time to develop. First a series of small holes will appear on the head of the goldfish then mucus will seep out through the holes and the fish’s slime coating will start to come off. If this disease is caught early there is a chance that the fish just might survive. The first step to treating hole in the head disease is to isolate the diseased goldfish to a hospital tank with fresh, clean water. There is a water conditioner called Stress Coat that contains Aloe Vera which promotes healing and will replace the slime coat for your goldfish. Be sure that your goldfish is getting a well balanced diet with all the important vitamins and nutrients. Sometimes these treatments along with the addition of salt to the aquarium can be enough treatment to stop the progression of this disease. Otherwise a radical treatment of Metronidazole can be a last resort. This treatment is used to kill the specific bacteria and parasites that are believed to cause Hole in the head disease but are not proven.

  • Costia

    Costia is a disease caused by quick moving parasites. This disease exhibits symptoms that look like slime patches on the skin of the infected goldfish. The skin turns a milky color and the fish might also have difficulty breathing. This condition, if not dealt with swiftly will potentially lead to death. Treatment starts with raising the temperature in the aquarium to 80 - 83°F (~ 27 - 28°C) then treating with medication. There are two medications that are equally effective but each one has a different side effect. Copper Safe works well but can be very toxic to certain fish. Be sure to read the label to see if your fish are able to handle this treatment before using it. Acriflavine is the other medicine that works well but the fact that it can cause sterility in fish might not make this an acceptable treatment for your aquarium.

  • Trichodina

    Trichodina is a parasite that implants itself in the skin and gills of goldfish and other freshwater fish causing the fish’s skin to become itchy and irritated. This disease is very noticeable because you will see the goldfish scratching against surfaces which can cause ulcers and stress. This condition is usually due to poor water quality with high bacteria content. This parasite feeds on bacteria so improvement of water quality is one of the main solutions to this problem. Salt can also be a very effective solution except that there is a strain of this parasite that has developed a resistance to salinity. In this case use Quick Cure as directed and the trichodina should be cured.

  • Velvet

    Velvet is a parasite that infects the skin of both fresh and salt water fish. It is also known as Gold Dust Disease because of the gold, dust-like appearance which also gives the skin of the fish a velvety-looking texture. The infected fish will scratch against surfaces, have difficulty breathing, and even become lethargic. The first course of action to treating this disease is a partial water change. Fresh, clean water with dim aquarium lighting and a little bit of aquarium salt could cure minor cases of velvet if the condition is caught quickly enough. Otherwise, medicines such as Quick Cure or Copper Safe can be added to the aquarium to eradicate the parasite completely.

  • Body and gill flukes

    Body and gill flukes or Shimmies are parasites like small worms that infect either the body or the gills, or both at the same time. The flukes that infect the gills are different from the flukes that infect the body of the goldfish because they each reproduce differently. The gill flukes lay eggs in the substrate while the body flukes give birth to live young. It is more difficult to completely get rid of gill flukes because of their egg-laying reproduction. An infected fish will scratch against surfaces, have an extra thick slime coat, have difficulty breathing, and can sometimes become lethargic. Potassium Permanganate is one treatment that can be used for flukes but it can get fairly expensive. Quick cure is another possible treatment but is not always considered to be as effective. Repeat treatments at least two more times after initial treatment to ensure all gill fluke eggs are killed, otherwise the problem will persist.

  • Anchor worm

    Anchor worm is a highly contagious parasite that infects fish even when they are not weakened due to stress. This parasite will burrow into the skin, gills or even the eyes of a goldfish or other freshwater fish causing skin irritations. They get to be about a quarter of an inch in length so they are very visible to the eye without a microscope. The worms can burrow deep down into the organs of the fish if the problem is not taken care of quickly enough. Treatment for anchor worm can be as simple as pulling out the worm with a pair of tweezers or treating with a medicine called Anchors Away, which is especially effective when it comes to removing anchor worms and other parasites.

  • Fish lice

    Fish lice are parasites that can be seen without a microscope and has the freedom to move around on the goldfish. The fish will scratch against surfaces which can cause skin irritation and sores giving bacteria breeding ground to cause secondary infections to the fish. This very contagious parasite will lay multitudes of eggs each of which will hatch and find hosts of their own. Anchors Away is a very effective treatment for fish lice. Repeat treatments are highly necessary because this medication will not kill lice in their egg form. After the lice seem to be completely gone it has been known to reappear due to un-hatched eggs so be sure to treat, treat and re-treat very diligently.

  • Columnaris

    Columnaris is also known as cotton mouth disease because of the white spots that appear on the mouth of the goldfish and other freshwater fish. Not only do these cotton-like growths infect the mouth area but it can also infect scales and fins. It is easy to mistake this condition for fungal infections but it is in fact bacteria that are named for its column-like shape. Clean and fresh water and aquarium salt is one treatment for columnaris but copper sulfate can be much more effective if needed.

  • Melanophore Migration

    Melanophore Migration is characterized by black spots forming on the otherwise healthy goldfish. The melanophore is a pigment containing cell that can control how dark or light the skin pigment will be. It is because of melanophore cells that an animal can change its skin colour to camouflage itself. This condition can come about when the goldfish is experiencing stress due to poor water quality, or it can be a secondary infection inflicted by parasite infestation. A simple water change can be the solution to curing this ailment. Once the aquarium water is clean you will have to wait awhile for the black spots to disappear.

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