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Disease Descriptions

Parasitic Infestations
Freshwater Ich aka Ick aka White Spot Disease:
  • Symptoms: Fish look like they have little white salt granuals on them and may scratch against objects in the tank.

    Ichthyopthirius Multifiliis (Ich) is caused by a protozoan. It has been found that Ich can lie dormant at the base of fins on a healthy fish until they are in a period of stress. The only time that the Ich is susceptible to treatment is during the "free swimming stage" The developed cyst will fall from the host fish and the cyst will then "hatch" releasing hundreds if not thousands of new parasites free to infect other fish. This disease is highly dependent on the temperature of the water the fish are being kept in.

    Gill Flukes:

  • Symptoms: Fish gasps for air at the water's surface. The gills may be pumping open and closed rapidly. Excess mucus or puss may exude from the gills. The gills may appear red and inflamed, bleeding or slimy and parts of the gills may be eaten away. The fish may scrape against objects to get the flukes off.

    These parasitic flatworms will appear as tiny worms, but are very difficult to see. Gill Flukes are contagious and should be treated immediately. Gill Fluke eggs are resistant to medications, but the larvae and adults are susceptible. This disease is most common in younger fish and fry, who are more susceptible to the parasite.

    Skin Flukes:

  • Symptoms: The fish may scrape against objects to get the flukes off, fading of colors. Fish becomes mucus-covered, skin becomes red in places, fins may begin to fray.


  • Symptoms: Velvet Disease has the appearance of a fine dusting of yellow or gold coloring covering a fish's body, fins, or gills. Depending on the color of the fish it can be difficult at best to see it. Sometimes checking a fish's transparent fins is often the best way to check for Velvet.

    Velvet Disease has a lifecycle like that of Ich. Velvet also uses light as an alternate energy source, shading your tank may also help speed recovery.


  • Symptoms: Include frayed fins, milky or opaque skin and fins, skin erosion, excess mucus, and scratching on objects in the aquarium. In the early stages of infection fish may be seen scratching on ornaments, rocks, or gravel. In the later stages, fish are often seen hanging near power filter outlets, pumping their gills, in an attempt to get oxygen. Fish may rest motionless at the bottom of the aquarium or pond.

    Trichodina is a ciliated protozoan parasite that infests most freshwater tropical fish, goldfish, koi, and saltwater fish. Trichodina is too small to be seen without a microscope, up to 100 microns in diameter. Trichodina infestations are "slow-moving," gradually affecting fish if untreated.


  • Symptoms: Clamped fins, listlessness, hanging at the surface and gasping may be seen. A whitish film covers the skin primarily around the head and dorsal fin. The gill membrane will lose its normal pinkish coloration taking on a much duller gray or whitish look. The damage to the gills can be irreversible. In advanced cases the skin becomes enflamed eventually shredding and falling off in strips.

    The parasite initially attacks injured fish but in crowded aquariums will host on healthy fish slowly debilitating its host. Dead fish must be removed quickly as the cell leaves the body within two hours.

    Miscellaneous Illnesses & Bacterial Infections

    Exophthalmia- (Popeye):

  • Symptom: Bulging eyes.

    Popeye or Corneybacteriosis will cause swelling in the head of the fish causing the eyes to protrude outwards. Popeye is a condition and not an actual disease. It can affect one eye or both. Possible causes are poor water quality, trauma, internal bacterial infection and also Gas Bubble Disease.

    Gas Bubble Disease:

  • Symptoms: Include the appearance of Popeye. It is possible to see the formation of these gas "bubbles" which could even be classified as blisters under the skin located anywhere on the fishes body including the fins. If these bubbles move to the blood stream they can be fatal.

    The condition is brought on by oversaturation of oxygen in the fish tank. Specifically the balance of dissolved gases being upset by the over production of oxygen.

    Hypoxia: (Oxygen Starvation)

  • Symptoms: Lethargy and a tendency for the fish to gasp at the water surface and congregate around water returns.

    Many of these signs are the same as for a gill problem so a test for Dissolved Oxygen has to be made to be conclusive. Running a test for dissolved oxygen content should be conducted in early morning hours since that is the time of day when levels are usually lowest and they are normally highest in late afternoon.


  • Symptoms: Ragged or disintegrating fins.

    Finrot can occur as a result of an injury, as a secondary infection once the fish has been weakened by another disease, or in some cases, as a primary infection (bacterial). As a bacterial infection or as a fungal infection, the fins or the tail will rot more evenly and is more likely to produce a white 'edge'. Sometimes, both types of infection are seen together. Infection is commonly brought on by bad water conditions, injury, poor diet. Finrot starts at the edge of the fins, and destroys more and more tissue until it reaches the fin base. If it does reach the fin base, the fish will never be able to regenerate the lost tissue. At this point, the disease may attack the fish's body directly.


  • Symptoms: Fish may appear to be suffering with finrot. Raised bumps underneath the scales. In advanced cases these bumps may rupture releasing fluid and may also have leave large bleeding ulcers. There may also be hemorrhages noticeable in the underlaying tissue.

    Aeromonas bacterium, which infects a fish via skin parasites or when it ingests feces from infected fishes or feeds on the remains of dead fish.

    Bacterial Septicemia:

  • Symptoms: Fish may have reddening at fin bases, blood streaks throughout the fins and body. Lethargic or listless behavior and lack of appetite may also be present.

    Bacterial infection often brought on by poor water quality or as a result of the fish being weakened due to parasitic infestations.


  • Symptoms: Fish's abdomen becomes unusually large and swollen, scales may stick out resembling that of a pine cone. The fish may have what appears to be Popeye or the eyes may actually cave in. Long pale feces, reddening of the vent area and body ulcers may be present along and below the lateral line of the fish. The fish will lose its appetite and show no interest in eating. In advanced cases, skin discoloration and scale loss may also occur.

    Dropsy is not, in itself, a specific disease, but rather refers to a condition. A sudden swelling of the abdomen (scales may stick out) is known as acute dropsy while a slow swelling of the abdomen is known as chronic dropsy. The actual cause of this swelling could be indicitive of any one of several conditions:

    Neon Tetra Disease:

  • Symptoms: Restlessness, Fish begins to lose coloration, Cysts develop and body may become lumpy, Fish has difficulty swimming, Spine may become curved in advanced cases, Secondary conditions such as fin rot and bloating are common.

    Neon Tetra disease is more common than many aquarium enthusiasts realize, and affects species beyond Neon Tetras. Named after the fish that it was first identified in, the disease strikes members of the tetra family most often. However, other popular families of aquarium fish are not immune.
    The disease cycle begins when parasitic spores enter the fish after it consumes infected material, such as the bodies of dead fish, or live food such as tubifex, which may serve as intermediate hosts. Once in the intestinal tract, the newly hatched embryos burrow through the intestinal wall and produce cysts within the muscle tissue. Muscles bearing the cysts begin to die, and the necrotic tissue becomes pale, eventually turning white in color generally starting within the color band and areas along the spine. It is not unusual for the body of the fish to have a lumpy appearance as the cysts deform the muscles.

    Swim Bladder Disease:

  • Symptoms: A fish will lose its equilibrium causing the fish to swim erratically or float upside-down or sideways.

    Buoyancy problems are caused by a wide variety of disorders. Deformed bladder, parasite infestation, bacterial infections and tuberculosis. Two of the more common reasons are either constipation or dry food is eaten quickly and swells up in the fish's intestine and keeps the fish from controlling its swim bladder properly. Isolating the fish to a hospital tank in which the water is shallow is a wise thing to do until the cause can be determined. The shallow water also provides relief for the fish.

    Toxin Poisoning:

  • Symptoms: Cloudy eyes, Blood Streaks, Acting listless and or fish who are darting and swirling.

    Cloudy eyes, Bloody patches and sluggishness, are indications that metallic poisoning may have occured. Also, using aerosol sprays directly around your tanks can have an adverse affect. The same with having soap residue and perfume on your skin that you expose to the tank water. If in doubt, as to what is wrong always suspect poisonious toxins.

    Osmotic Shock:

  • Symptoms: Fish gasps for air at the water's surface, gills open and close rapidly, or have purple gills. Also, fish may become inactive.

    Fish actively maintain a natural balance of electrolytes in their body fluids. Electrolytes such as potassium, sodium, chloride, calcium, and magnesium are removed from the water by chloride cells located in the gills. These electrolytes are essential for the uptake of oxygen and release of carbon dioxide and ammonium across gill membranes. The lack of electrolytes can cause serious health problems to the fish. Osmotic shock interrupts healthy gill function by reducing the intake of oxygen and the release of carbon dioxide and ammonium from the fish. This can lead to the loss of electrolytes through the gills. Also, a fish who has had their slime coat disturbed can lose electrolytes through their skin increasing the possibility of a fish contracting Osmotic Shock.


  • Symptoms: Ulcerous wounds on body, faded colors, fins clamped shut, weight loss or wasting, pop-eye

    A fish may exhibit wasting or other loss of weight for no apparent reason. A tubercular fish has a normal appetite, but as internal organs become damaged by the disease, the fish slowly loses weight to the point where the fish's head will appear too big for her body. If a nodule forms under the fish's eye, it may protrude, causing pop-eye. These nodules on other parts of the body develop into ulcers. Unfortunately, by the time the symptoms become noticeable, the fish has been infected internally for quite some time.

    **Tuberculosis is becoming a more common occurrence in recent years, and is an especially serious disease. It is very contageous, and in some cases, it is also transmittable and dangerous to humans. The utmost care must be given to prevent the spread of this disease to humans or other fish. If you suspect your fish may be afflicted with this disease, remove them immediately from the tank. Anytime you have any open sores or cuts on your hands, wear plastic gloves regardless if you suspect Tuberculosis might be present or not. Unfortunately, Tuberculosis is very difficult to treat in fish, and is most often fatal.

    Columnaris: (Mouth Fungus)

  • Symptoms: Grayish white stringy material or patches covering most of the body but particularly in the mouth area. In advanced cases I have seen the patches located just inside the mouth affecting their ability to consume food.. If not treated these patches can turn into sores. If the disease infects the gills, gill swelling will occur, gill filaments may stick together and excessive mucus may develop in the gill area. A sign of this is rapid gill movement and the fish gasping.

    Columnaris is often confused with a true fungus infection. Columnaris disease is caused by a bacteria Flexibacter columnaris and not by fungus. Columnaris can be highly contagious so any suspected fish should be isolated as soon as possible to begin treatment.

    Fungal Infections

    True Fungus Infection:
    Fungal infections usually occur as a secondary infection, invading tissue already damaged by bacterial and parasitic diseases. Fungus also attacks fish that have been weakened by rough handling, shipping, exposure to ammonia and nitrite, improper netting, and malnutrition. Fungal pathogens use digestive enzymes to feed on the fish tissue. The enzymes damage nearby healthy tissue, allowing the disease to spread.

  • Symptoms: White, gray or brown tufts of cotton-like material (similar in appearance to mold found on fruit, bread or cheese except on a fish is usually white) found on the fins, tail and body of the fish. Fungal infections are opportunistic and are not contagious to otherwise healthy fish.

    Common name: Cottonmouth disease, Cotton-wool disease

  • Symptoms: Include white cottony growth on fins, skin, and mouth of fish. The cotton-like growth may appear greenish if algae collect in the fungal filaments.

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