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The Nature of Disease in Ornamental Pond Fish
The Role of Temperature
Springtime brings about important changes in the dynamics of your garden pond. Along with greening of pond plants and the revival of the fish, we often see an increase in fish disease - rotting fins, ulcerations of the skin and sometimes even death. What about spring brings on disease? Temperature is the most significant factor. During the spring, temperatures can vary considerably from day to day. Ideally, pond water would rise incrementally each day until optimal - 77° F for the fish - summer temperatures are reached. The sometimes drastic fluctuations in air temperature cause fluctuations in water temperature that directly affect fish health.

Sharing the pond environment with goldfish, koi and plants are a number of bacterial, fungal and viral pathogens. Among these, the bacterium, Aeromonas, is thought to be a major player. Some researchers believe that a virus, Rhabdovirus carpio, is the initial invader and that Aeromonas is a secondary pathogen following the viral attack. Whatever the initial and secondary organisms, these two are ubiquitous to freshwater environments and are detected at outbreaks of ‘Ulcer Disease,’ also referred to as ‘Koi Ucler Disease.’ At water temperatures of 55° F and below, the fish are dormant - feeding has ceased, metabolism has slowed, and waste is significantly diminished. The beneficial bacteria in the filtration system have reduced in number correspondingly to the reduced food source from the fish. In this low temperature range the fish pathogens are also dormant.

As spring approaches water temperatures in the pond begin to warm. At water temperatures between 48-62° F, disease-causing pathogens begin to flourish and are most capable of causing disease. Fluctuations in air temperature in the spring tend hold the water temperature in the optimal range for these organisms for a longer period of time. Just as the pathogens reach their peak of activity, the fish are at their weakest. Having fasted all winter, the fish have nearly exhausted their fat reserves and their immune systems are seriously compromised. Skin eruptions may begin to appear, the tail and fins may become ragged.

Other Contributing Factors
A number of factors contribute to the spread and persistence of ulcer disease. The amazing popularity of pond keeping has significantly increased the demand for outdoor fish, which has, in turn, increased production by fish farms worldwide. It may be that this overproduction has resulted in poor husbandry practices allowing the pathogens to remain in fish populations through many generations. Genetics certainly plays a role in the spread and persistence of this disease. Strict selection for desirable characteristics by Japanese and other breeders may reduce the vigor in breeding lines making fish less hardy and more susceptible to disease. It is a common misconception that koi and goldfish are merely carp. The animals we see in our ponds today differ dramatically both physically and genetically from their carp ancestors.

Success of a pathogen also depends on its ability to develop resistance to medications designed to interrupt its life cycle. With the widespread use of ‘shotgun’ antibiotic administration, the causative organisms have become more and more resistant to treatment. There is no question that standard medications are becoming less effective against common diseases we see in our aquariums and ponds. Considerable research is under way to develop new, more specific medications to treat the constantly evolving stains of bacteria, parasites and fungi that prey on our pets.

• • Disease Management
The first line of defense against disease is prevention. Prevention of ulcer disease and other problems actually begins the moment you introduce fish into your pond. As always, the best cure for disease is prevention at the farm level and in the home pond. Good filtration, regular water changes, good sanitation habits and careful observation are the best preventative measures. Using Winter Prep and Protect Plus by Tropical Science also helps ward off potential problems.

Stocking your pond
Select good, disease-free stock from reputable, responsible dealers. Look at the facility, talk to the keepers. Good dealers with healthy stock maintain separate quarantine and treatment facilities. They are proud of their animals and their operations and do not hesitate to share their insight with you. Good dealers take the extra steps to adhere to good sanitation and husbandry practices. Follow their advice about kinds and numbers of fish and regular water testing. For obvious reasons, avoid stock from mass retailers.
See Solution 15b

Even though your dream was to have a ‘natural’ water garden beautifully blended into your landscape, the reality is - there’s nothing ‘natural’ about a hole you’ve dug in your yard and lined with a big piece of rubber. Forget about your dream and think about what’s best for your fish. Unlike land animals, fish are trapped in their environment and cannot escape pollution and toxins. The point of filtration is to keep water clean and safe, not to keep it nice to look at. Good filtration, however, will do both. See Solution 4

Once the pond has completed the
Nitrogen Cycle, regular monitoring of ammonia, nitrite, pH and nitrate is essential to prevent disease. Ammonia and nitrite are caustic and burn the gills and other delicate membranes that protect the fish. Gills and membranes are also affected by pH values that are out of balance. Any of these factors can cause stress, lower resistance and leave fish with an increased risk of assault by ever-present pathogens. Test, or have your water tested frequently. The expense is minimal compared to the losses that can occur without testing.

Few factors figure into good health like nutrition. Good nutrition builds healthy bones and tissues, reduces stress and strengthens the immune system in fish. Fish require high quality protein and stabilized vitamins for adequate growth. Cheap, low quality and poorly formulated foods contribute to fatty liver disease, reduced water quality and lower resistance to disease. Foods prepared for mass aquaculture (fish farming) are formulated to fatten fish over a relatively short period of time rather than sustain growth throughout the life of a fish. These foods often contain additives that promote deposition of fat rather than muscle. Read fish food labels and feed a variety of foods to ensure that your fish receive essential nutrients for sustained growth and long-term good health. OSI, Ocean Nutrition and Total Koi manufacture the best foods available. See Solution 18

Know your fish. Watch their habits. Pay close attention to their gills, their scales and skin. Learn the configuration of healthy fish and how they behave. Feeding is a good time to get a better look at their bellies, mouths and fins. Fish in a relatively stress-free environment are friendlier and spend more time near the surface giving you a much better chance to observe them for redness, ulcers, mouth and fin problems. Usually, by the time symptoms become obvious on the body, the disease is well underway. The earlier you detect an illness, determine the cause and begin treatment, the better chance the fish have to recover. Observe symptoms carefully and report them accurately to your dealer.

Despite your efforts and good intentions, fish will get sick and require medication. Be aware - many medications on the market simply are not effective against disease. Unfortunately, many of these so-called medications are sold to unsuspecting customers, administered, given a week or two to work and the fish are still sick. Precious time is lost and the fish are in worse shape than before the treatment was begun. Aquatic Connection stocks and recommends a very select group of medications for ponds which have been used by our company in a variety of applications or by well-recognized breeders or wholesalers in the koi trade. When used in properly filtered and maintained ponds, these medications should solve most disease problems if symptoms are noticed soon enough.

Diseases in pond fish are generally caused by viruses, bacteria, fungi and/or parasites. Infection by one of these groups readies the fish for secondary or tertiary attacks by another group. Bacterial infections are frequently secondary infections resulting from wounds from handling or wounds caused from parasites. If this is the case, treatment should address both parasite and bacteria. All disease problems are compounded by poor water conditions. Continued fungal problems are always related to poor water quality. Once again, ignoring water quality problems is equal to pouring medications into the yard. Fish that are severely affected may die regardless of treatment.

Medications are lethal if used improperly. Dosing and pond volume must be exact.
If medication is used directly in the pond, it should be added to an area of
heavy water movement to mix it quickly.

  • Ideally, affected fish should be treated in a holding tank separate from the pond to avoid disruption of the filtration system. In setting up treatment tanks or treating the pond directly, follow these principles:
    • Keep the tank (pond) and fish shaded.
    Pieces of styrofoam work well to provide shade.
    • Get the fish to eat.
    Krill soaked in vitamins and tetracycline and/or Pipzine (see below) works wonders to stimulate appetite.
    • Increase aeration with an airstone at the time of treatment.
    • Add salt at a concentration of 0.3%.
    Use Sea Salt or uniodized table salt. Salt is effective in two ways: 1) salt kills pathogens directly; or 2) changes the osmotic potential of pathogen membranes reducing their ability to affect the fish. (See below.)

• • General Purpose Treatments
As described earlier, once a particular disease is underway, a number of secondary pathogens usually invade the fish and the disease situation becomes more complicated. Since many of the diseases present with similar symptoms and lesions and may be caused by a number of different organisms, without microscopic confirmation, specific diagnoses are difficult to make. The preventatives and medications that follow have proven effective against the most common infections and infestations that occur in koi and goldfish.

• Quarantine
Once signs of disease appear, it is advisable to move the affected fish to a quarantine system. Quarantine systems isolate sick fish from healthy fish, are of known volume for easier dosing of medication, are easier to manage, and, in the long run, reduce stress to both the fish and the keeper. Repeated chasing and netting sick fish can further weaken the fish and exacerbate the disease.

• Medicated Foods
Begin feeding medicated foods in early spring as soon as your fish are ready to accept food. Since spring is an especially dangerous time and fish are more susceptible to disease, feeding exclusively medicated foods may head off problems.
Oxymanna and Romet Medicated Sinking Pellets are good medicated foods to begin feeding in early spring. Using WG Pro Tech Coat also helps ward off potential problems.

• Salt
Salt is an excellent preventative, a good choice if diagnosis is unclear and it can be used in combination with other medications. The following is a list of the benefits of salt in the pond:
Does no harm to majority of fish species;
Eliminates most of the parasites common to ponds;
Is not affected by sunlight or organics in the water;
Imposes no health risk to humans;
Does not harm the biological filter;
Does not reduce the dissolved oxygen in the water;
Reduces nitrite toxicity;
Enhances the fishes’ natural slime coat; and
Helps prevent bacterial infections.

The major disadvantage to adding salt to your pond is its effect on plants and invertebrates. It kills Anacharis, Cabomba and snails at the recommended treatment levels. Other plants may suffer yellowing and loss of leaves or stems. Remove sensitive plants and invertebrates before adding salt.

Sea Salt or aquarium salt works best, and is safest, but other options may be explored for large ponds.
CrystalSea Saltwater Mix or table salt can be used with success but should be added slowly to prevent a sharp rise in pH. The added minerals in seasalt mixes is thought to have positive effects on the koi and other pond fish.

Dose at 3 teaspoons per gallon of pond water or 3 pounds per 100 gallons in three equal parts over 3 days for the first treatment. Never pour salt directly onto the fish. The salinity, or specific gravity, can be measured with a
Crystal Sea Hydrometer. Your dealer may be able to test your salinity with a more accurate refractometer. Treat for 2 to 3 weeks or 14-21 days and continue to feed medicated foods.
Recommended Salt Concentrations:
1.004 or 7ppt reading on a hydrometer for treatment of fish in the pond.
1.002 or 3ppt to avoid damage to plant life.
if fish are treated in quarantine from the pond, salt concentrations up to 10ppt are effective.
successive water changes with clear, dechlorinated water restores the salinity to 0.

Change 25-75% of the water after the last day of treatment using a high quality dechlorinator designed for pond use, such as
Water Garden Chlorinex by Kent Marine. Following the water change, add Water Garden ProTech Coat by Kent Marine.

If treating fish in a separate quarantine tank, water changes may have to be done if ammonia reaches toxic levels. Remember to bring salt level back to the desired range following the water change. Only add the amount of salt needed to treat the amount of water taken out and use dechlorinator.

  • Diseases cannot be cured if:
    fish are crowded
    ammonia reads in any concentration
    nitrites are not under control
    fish are fed a poor diet
    parasites exist on the fish
    rotting leaves or dead fish are left in the pond
    water temperature is below 65° F
    fish are not eating
    water is turbid, milky, or foul smelling

Specific Purpose Treatments
• External Parasites
Parasite infestations may or may not be visible on the fish making diagnosis difficult. Anchor worm and Fish Lice are visible to the naked eye but others, such as Trichodina, are not and must be verified by microscopic examination. Often we assume scratching and thrashing are symptomatic of parasite infestations.

This medication is effective against Anchor Worm, Fish Lice and other external parasites. F.L.A.W. is packaged as a pre-measured powder in a bottle. Fill the bottle with tap water to the neck, replace the cap and shake well. Add 1 drop per gallon for 3 days. If, on the third day following the last treatment, parasites reappear on the fish, repeat the treatment. F.L.A.W. may affect invertebrates.

Fluke Tabs (Aquarium Products)
Fluke Tabs is effective against the most stubborn parasites, particularly body flukes and gill flukes. Follow instructions carefully.

Pond Clout (Aquarium Products)
This antiparasitic is effective against anchor worm and fish lice. Follow instructions carefully and retreat as necessary.

Malachite Plus (Marine Enterprises)
Malachite Plus is a broad spectrum anti-parasitic agent that will not harm plants. Primarily used for parasites, it has also proven effective against some common fungal infestations and some bacterial infections, though not the ideal medication against bacteria.

Prior to treatment do a 25-50% water change, if possible. Organic material in the pond reduces the product’s effectiveness. Remove any carbon filtration. Treat in the evening if possible since light causes rapid oxidation of the medication.

Dose at 1 drop of Malachite Plus per gallon. (1ml = 20 drops.) We recommend dosing at one-third the strength suggested on the bottle. Measure Malachite Plus and other liquid medications into a separate container to avoid accidental overdose. Maintain aggressive water circulation with an air pump and airstone. If fish show signs of stress, do a partial water change and treat at a lower dose, especially if you do not know the exact volume of the pond. Remember, overdosing kills fish. Malachite Plus reduces dissolved oxygen levels and care should be taken when the pond water temperature is above 85°F degrees. The ideal water temperature for treatment is 65-80° F. Continue to feed medicated food.

CAUTION - Malachite Plus contains formalin, a known carcinogen. Avoid contact with skin, keep away from children, and use in ventilated or outdoor environment. Follow the instructions on the bottle in case of contact with skin, eyes or mouth. Malachite Plus stains anything it contacts.

• Wounds, Ulcers, Bacterial Infections, Fungal Infestations
Disease Dip
Disease Dip is a disinfectant that promotes healing of wounds, abrasions and scrapes. Used as a preventative, Disease Dip is effective against ulcerations. If used as a topical disinfectant, fish must be netted, carefully held in the net and the medication swabbed onto the affected area. Place 1 or 2 drops directly onto the wound. Treatment may be repeated daily until the wound heals. Continue to feed medicated food. Exercise care to keep stress at a minimum. If wounds are large and numerous, Dip-A-Way may be a better treatment.

This medication is effective against fungal infestations, white cottony patches, ragged and frayed fins and parasitic infestations. Shake bottle well and add 1 teaspoon of Hydroplex per 8oz of clean, dechlorinated water in a clean bucket. The size of the fish determines water depth. Net the affected fish, dip quickly in the solution and return the fish to either the pond or the quarantine tank. Treatment can be administered daily until the problem resolves. Continue to feed medicated food. Exercise care to keep stress at a minimum.

These antibiotics are effective against red streaks in fins, hemorrhaging, dropsy, fin and tail rot, inflamed gills, skin ulcers, and some fungal infestations. Both can be used in small ponds but treatment in a quarantine tank is better. Dose at one capsule per 10 gallons of water for 3-5 treatments. Continue to feed medicated food. Repeat the full treatment after 3 days if necessary.

Oxolinic Acid
Oxolinic Acid is absorbed through the gills into the bloodstream and is effective against gram-negative bacteria, ulcerations, abdominal bloat, dropsy, white body slime, cloudy eyes, furunculosis and Columnaris. We recommend this medication only for a quarantine tank and it should be used as the sole medication during treatment. Oxolinic Acid affects invertebrates. Remove carbon filters before treatment. Dosage: open and empty one capsule per 40 gallons. If symptoms persist, treat again in two days. Continue to feed medicated food.

Fungus Eliminator (Jungle Laboratories)
Fungus Eliminator is effective against cotton fungus (Columnaris,) open red sores (furunculosis), red streaks in fins and body (hemorrhagic septicemia), gray body slime (Costia), dropsy, gill disease, fin and tail rot and cloudy eyes.

Before treatment, change 25% of the water and dose with 1 teaspoon per 5 gallons, or 1 cup per 240 gallons. Continue to feed medicated food. Clean measuring utensils after use.
Tetracycline is best used in a quarantine tank and is an effective treatment for mouth and body fungus, frayed fins and tail, skin ulcers and open sores, red body sores and patches, gill disease and Columnaris in goldfish and koi. Dose with one capsule per 10 gallons. Treat every other day for 5 days and repeat full treatment after three days if necessary. Continue to feed medicated food.
Effective against internal parasites, Metronidazole is used when fish show signs of weight loss or wasting, pinched in bellies, color loss and unexplained death. Since this medication does not affect the biological filter, it can be added directly to the pond at a dose of 1 capsule per 10 gallons. Treat every other day for 5 days. Repeat treatment after the third day if necessary.

Furazone Green
Furazone Green is an excellent choice for hemorraghing, open sores, fin and tail rot, gill disease, furunculosis, red patches and streaks common in goldfish and koi. Dose at 1 capsule per 10 gallons every other day for 5 days. Repeat full treatment after the third day if necessary. Continue to feed medicated food.
Trimethoprin Sulfa
This chemical is one of several agents added to foods to give them medicinal value. It is available from veterinarians and can also be used as a bath to treat bacterial infections and ulcers. It is uncertain what effects it has on biological filters so it is safer to use in a quarantine system.

Trimethoprin sulfa is mixed at 1gram per 10 gallons of clean, dechlorinated water. Place affected fish in this solution for 6-8 hours then return them to the quarantine system. Optimal temperature for the bath is 75° F. Treatment can be repeated 3-4 times with a fresh solution.
Increasingly, veterinarians are administering injectable antibiotics to ornamental fish with good success. Since treatment involves repeated injections, the cost can be prohibitive so this treatment must be weighed against the value keepers place on their livestock. Other injectables are in active testing phases and may become widespread in the near future.

•• We cannot be responsible for fish loss due to treatments outlined on this site.
We encourage you to buy healthy livestock from reputable dealers, observe fish carefully at regular intervals and test your water frequently for problems.
Prevention is always your first line of defense against disease. •• 
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