Fish Disease Diagnostic Information

Bacterial Infections: Inactivity, loss of color, frayed fins, bloated body, cloudy eyes, open sores, abscesses, red streaks throughout body, reddening or inflammation of the skin, fins or internal organs, bulging eyes, difficulty breathing.

Fungal Infections (often secondary to another type of illness):Erratic swimming, darting, scratching, visible cotton-like tufts on skin, eyes, or mouth.

Parasitic Infections: Inactivity, loss of appetite, excess mucus or film on body, visible spots or worms, rapid breathing, scratching.

SymptomsDiagnosisTreatment
Grayish-white film on skin, damaged fins, ulcers, yellow to gray patches on gills, tissue on head may be eaten away.Columnaris (Cotton Wool Disease)Must be treated immediately with Over-the-counter antibiotic medications. Very contagious disinfect tank, rocks, net, etc.
Swelling of head, bulging eyes.CorneybacteriosisOTC antibiotics such as penicillin and tetracycline.
Swelling of abdomen, raised scales around swollen area.Dropsy (Malawi Bloat) may be caused by internal bacterial infection (if swelling is sudden), parasites, or cancer (if swelling is gradual).Add 1/8 teaspoon of Epsom salt for every 5 gallons of water and monitor for two weeks. Check for signs of bacterial infection or parasites for further treatment.
Ragged or decaying fins.FinrotCheck pH and correct as needed. If level is normal, use OTC antibiotic for fin or tail rot.
Inactivity, loss of color or appetite, weight loss, skin defects.Fish TuberculosisHuman strength TB medication may help in early stages. Contagious disinfect tank, rocks, net, etc. to prevent transmission. Wash hands and surfaces well.
Erratic swimming, bloating or swelling in body, black patches on body or fins.Myxobacteriosis — rareMedications, if any, are difficult to come by. Keep up on water maintenance to prevent it.
Sluggishness, lack of appetite, fin damage, reddish discoloration, bulging eyes, clamped finsSepticemiaAntibiotic treatment in food form is required.
White or gray fungus on eyes.CataractsOTC medication for fungus.
White or gray patches resembling cotton, excess mucus.Mouth or Body FungusOTC medication for fungus. Usually added to water, but may need direct application.
White cotton-like patches on fins, body, or mouth.True Fungus (Saprolegnia)OTC medication for fungus. Check for symptoms of other illnesses.
Small string-like worms visible on fish, or burrowed in skin.Anchor WormOver-the-counter medication for parasites.
Bluish-white film on body, strained breathing caused by gill damage, peeling skin.ChilodonellaSalt treatment (see below).
Weight loss, strained breathing.CopepodsOTC medication for parasites, also fungal treatment for possible secondary infection on damaged gills
White film, reddened areas on body, abnormal swimming, scratching, folded fins.Costia (Slime Disease)Must be treated quickly. Raise water temperature and use OTC medication for parasites. Salt treatment may work, as well.
Weight loss, abnormal swimming, generally looks very ill. Will accompany or follow leech infestation.Blood Flagellates (Sleeping Sickness) rareSalt treatment can be used to kill leeches, but may not cure flagellates.
Sluggishness, flashing, spider web lesions on skin, color loss, reddened fins, drooping fins, fin damage.Skin Flukes (Gyrodactylus)OTC medication for parasites
Lack of appetite, weight loss, small holes or eroding pits appearing in the head.Hole in Head Disease (Hexamita) more common in cichlidsOTC medication for Hole in Head Disease.
Scratching, white salt-like spots starting on head and spreading over whole body, rapid breathing, cloudiness on eyes or fins.Ich (Ichtyophthirius) very commonOTC medication for Ich or Ick.
Scratching, small worms hanging from body.LeechSalt treatment or OTC medication for parasites.
Scratching, green to brown lice (up to inch) visible on skin.LiceOTC treatment for parasites.
Erratic swimming, weight loss, loss of color.Neon Tetra Disease mostly affects tetras, danios, and barbsTreatment is difficult look for a medication that treats gram-negative bacteria or with nalidixic acid as the active ingredient.
Darting, scratching, small yellow to white spots dusting skin.OodiniumOTC treatment for parasites.
Cloudy appearance on skin, red patches on skin where parasite has bitten.Trichodina — predominately freshwaterSalt treatment.
Red or bloody gills, gasping for air.Ammonia PoisoningNo treatment. Regular water testing and maintenance will prevent it.
Small dark spots on fins and body.Black SpotOTC medication for parasites. Spots (cysts) may remain after treatment.
Cloudy white appearance to one or both eyes.Cloudy EyeCheck for symptoms of another illness like velvet, ich, or tuberculosis. Treat with OTC medication.
String of feces hanging from fish, swollen abdomen, sluggishness, disinterest in food, off-balance swimming.ConstipationStop feeding for 2-3 days and continue with a more varied diet including live and plant-based foods.
Small white spots that get larger over time possibly with black streaks.Fish PoxNo treatment. Keep up on water maintenance and symptoms should cease after about 10-12 weeks.
Difficulty swimming, swimming upside-down, floating, unable to surface. Do not confuse with swim bladder disease.FlipoverAir can be removed from swim bladder by a veterinarian. Surgery is also a possibility in larger fish. Check for signs of internal infection or parasites and treat as necessary.
Reddening on or under skin, sudden abnormal behavior.InflammationOTC antibiotic treatment.
Unusally bulging of one or both eyes.Pop-eye (Exophthalmia)OTC medication for bacterial infections and/or parasites. Check for other symptoms of bacterial or parasitic infections.
Fish struggles to swim, may float with head tipped down, or have difficulty surfacing, no balance, etc. May occur after eating.Swim Bladder DiseaseStop feeding for 3-4 days. If symptoms persist, feed the affected fish a small amount of fresh spinach or a green pea without the skin (laxatives).
Swelling or distention for internal tumors, external can be seen growing on skin.TumorsUsually incurable. Consult a veterinarian about potassium iodide treatment for thyroid tumors.
Sluggishness, lack of appetite, open sores with red edges, possible fin rot.UlcersOTC medication for bacterial infections.
Scratching, small gold to white spots, loss of color, weight loss, difficulty breathing due to gill damage.Velvet (Gold Dust Disease)OTC medication for parasites.

Salt Treatments:

Understand that while salt is frequently used as a treatment/preventative for sick fish, it is no guarantee. It can even be dangerous to some fish (for example, cory catfish).

There is nothing more important than maintaining a proper environment (temperature, water quality, aeration).

Basically, salt will strip or re-stimulate (depending upon the concentration) the slime coat produced by the fish, increasing antibodies and making bacteria, fungus, and parasites more vulnerable to medications such as antibiotics or fungicides.

The following salts can be used in a salt treatment for your fish: Aquarium, solar (without anti-caking additives), meat curing, sea, kosher, rock, pickling, and ice cream salts, or regular non-iodized table salt.

The additives mentioned above may include a type known as sodium ferrocyanide or yellow prussiate of soda. This is deadly to fish. The “cyanide” part should clue you in to that.

For a constant preventative treatment, use a low concentration of about .3%. This is equal to about 2.5 teaspoons per U.S. gallon of water. If you have live plants in your aquarium, you may want to consider about half that amount.

For a concentrated “dip” to be used in treatment of external parasites, the concentration should be 1%, or 7.5 teaspoons per U.S. gallon. You must be very careful when using these dips. All fish will react differently to salt treatments, and especially smaller fish must be monitored very closely. Generally this will be done in a hospital/quarantine tank, as water changes are the only way to remove salt from your main tank. The hospital/quarantine tank should be at least one gallon, with no rocks and only two or three plastic plants for security. The temperature should be kept between 75-80 degrees with good aeration. Dissolve your salt completely before adding your fish. Once you have put your fish into the water, watch it closely for signs of distress, such as rolling over. This may be as quickly as a few seconds with smaller or baby fish. Remove the fish at the first sign! Do not leave your fish in this solution longer than 30 minutes. Then place it in a container of aged water, preferably not taken from the main (still infected) tank. Give the tank a thorough cleaning while your fish recuperates.

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