Pond Fish Diseases

+ Diseases +rev 10/08

If your fish are dying or acting abnormally in the absence of water quality problems, you should suspect either parasites, or bacterial infections. The most common parasites that affect goldfish and koi are listed below. Treatment options are listed in order of preference.

Before starting any treatment, first eliminate the possibility of environmental factors that may be affecting your fish. Any treatment will be useless and will weaken and harm the other fish if you do not correct the water quality problems. It's best to isolate the fish in a separate container and apply treatments there.

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KHV Information Click Here 06/08

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Ick or Ich(whitespot)- Ick is one of the most common and widespread of all the fish diseases. It is characterized by tiny white spots the size of coarse sand or table salt. Its microscopic stage is round with a horseshoe shaped nucleus. The parasite cannot be killed in the Egg stage. Symptoms may appear before you see the white spots. They include flashing (rubbing their sides against the pond), lethargy, and loss of appetite. The treatment of choice for Ick is salt for 10-21 days, depending on the water temperature. Ick takes longer to clear in colder water.

Use Treatment # 2

Lernea (anchor worm)- Anchor worms resemble a short piece of thread coming from beneath a single scale. Koi infected with anchor worms very often develop ulcer sores due to the damage caused by the worms as they bury into the flesh of the fish. Be aware that anchor worms will not disappear immediately. The treatment may take a week or longer, according to the water temperature.

Use treatment #4 & #2

Argulus (fish lice) pair. Gravid female on left

Fish Lice (argulus)- Fish lice are sometimes mistaken for a small patch of green algae on the fish. After looking closer, you will see that it is a round "bug" that is a little larger than a pencil lead. As with anchor worms, fish lice make little holes in the fish, making them vulnerable to bacterial infections.

Use treatment #4

Costia- Costia are microscopic parasites that attack the skin and/or gills of the fish. Symptoms include loss of appetite, listlessness, flashing, and excess slime production.

Treatment options in order of preference are #2 #1 & #3

Chilodonella- Like costia, chilodonella are microscopic. They are most usually present in colder water (40-50 degrees). Symptoms are similar to those caused by costia.

Treatment options in order of preference are # 2 #1 & #3

Flukes (Gyrodactylus and dactylogyrus)- Flukes are the most commonly found parasite on koi and goldfish. High numbers can cause serious damage. Symptoms include flashing, gasping at the surface, frayed fins, and death. Most cases of ulcer disease are preceded by fluke infestations.

Treatment options in order of preference are #3 & #1

Trichodina- Another microscopic parasite, trichodina is easily identifiable. It resembles a wagon wheel. Fish infected with trichodina often develop a gray film over the body in response to the infestation. Other symptoms include flashing, lethargy, and hanging at the surface.

Treatment options in order of preference are #3 & #1

Bacterial infections- It is important to remember that pathogenic bacteria are always present in our water and on our fish. They are a problem only when the fish are weakened by poor water quality or parasite infestations. So, before attempting to treat a bacterial infection, be sure that you correct any underlying problems first. Symptoms can include fin and tail erosion and fraying, redness of the tail, pectoral or anal fins, and red open sores (ulcer disease). The most effective remedy for most bacterial infections is feeding medicated food containing tetracycline, romet, or oxolinic acid for 10-14 days.

Ulcer disease- Ulcer disease is a particularly destructive bacterial disease. Seen on koi and goldfish, it starts out as a red or white pimple and quickly widens into a large hole or ulcer. It can advance all the way into the muscle of the fish. It is very important to catch this disease in its earliest stages. Anchor worms, fish lice, and flukes can all contribute to ulcer disease. Keeping your fish clear of these parasites is very important. Keep affected fish in salted water and feed medicated food containing oxolinic acid or romet. Individual sores can be swabbed with betadine to help them heal. Read More about Ulcers Advanced cases in valuable fish can warrant antibiotic injections, contact an experienced Veterinarian for assistance.

First Aid and Treatment Chart

Notes on salt: While table salt contains minute traces of Iodine which tends to cloud water which is especially noticeable in Aquariums, table salt can be used without fear in a pond. Even so, I recommend plain rock salt, or water softener salt from a standpoint of cost. Measurements of salt dosages should be carried out by weight, with table or teaspoon measurements used only in emergencies.

#1) SALT DIP- Add salt to water at 10 tablespoons per gallon or 8 pounds per 32 gallons. Dip fish in this solution for 3 to 5 minutes or until it starts to roll over. Repeat 2 more times at 12 hour intervals.

#2) SALT BATH- 0.3% to 0.6%, the recommended dosage is obtained by adding 3-6 teaspoons per gallon or 50 pounds of non-iodized salt per 1,000 gallons over a 3 day period. Salt should be removed by water changes, when the disease has run it's course.

#3) POTASSIUM PERMANGANATE- Read More Caution do not use in windy areas, as the chemical blowing into your eyes can cause blindness- Potassium permanganate is effective against all of the microscopic parasites listed above except Ick. If you suspect that your fish may have parasites, but you do not have access to a microscope to confirm your suspicions, potassium permanganate should be your first choice for treatment. It is more risky than salt, but only if you fail to measure your pond capacity in gallons and dosages accurately. Potassium permanganate will turn the water purple or pink when first added to the tank or pond. It will eventually turn brown, according to the amount of dissolved organics in the water. A 25% to 50% water change is recommended before beginning the treatment. Bypass the filter, ensure adequate aeration, and add potassium to the water at 6 grams (1 level teaspoon) per 800 gallons, In large systems, dissolve the crystals in warm water and distribute evenly around the pond or tank. Note the color of the water by submerging a white saucer 2-3 inches below the surface. If the color changes from purple/pink to brown/amber in less than 1 hour, re-dose at 1 teaspoon per 800 gallons. If the initial color change comes after 1 hour has elapsed, retreat at 1/2 teaspoon per 800 gallons. Monitor the color of the water for the next 10 hours. Whenever the color is brown, add more potassium at 1/2 teaspoon per 800 gallons. The key for effective treatment with potassium is to maintain the pink color in the water for 10 hours. After 10 hours, do another 50% water change. Adding de-chlorinators or hydrogen peroxide, will neutralize and de-color the potassium. Repeat the treatment in 3-4 days to ensure eradication of the parasites.

#4) DIMILIN-Read More - Also available as Jungle Lab Pond Anchors Away (tm) or Aquarium Pharmaceutical's Dimilin follow label directions.

Insecticidal Dimilin should be mixed with water @ 1 teaspoon per 2,000 gallons and applied every 30 to 60 days for control of anchor worms and fish lice. These parasites will not clear immediately.According to the water temperature and type, they will be eradicated anywhere from a few days to a few weeks.

Note--There are many more medications used and abused in the pond world, we have not listed any but the safest and most widely available to the average pond keeper. Medicines that are not available over the counter should be used with the advice of a licensed Veterinarian and are beyond the scope of this "First Aid" article.

WARNING: THE MEDICATIONS LISTED HERE ARE SAFE WHEN HANDLED PROPERLY. USE A DUST MASK, RUBBER GLOVES, AND SAFETY GLASSES WHEN HANDLING THESE CHEMICALS.