Aquarium Fish: News From The Warfront With Cryptocaryon Irritans, Part Three Of Five

by | Jan 15, 2004 | 0 comments

This is the third installment in a five part series. Part two covered the life cycle, how to identify Cryptocaryon irritans, symptoms of infection, adaptability of this parasite, the new challenge and prevention. Part three continues with sections covering those few consistently reliable methods of eradicating “ich” and some experimental treatments for its control.


Limited number of reliable treatments

There are many purported treatments for cryptocaryonosis. Unfortunately, the majority of these methods or therapies are only partially effective at best. There are currently only three proven, consistently reliable, treatments. These consist of copper treatment, salinity manipulation (i.e. hyposalinity) and the transfer method. Even the best treatments currently available have limitations and/or drawbacks.


Copper treatment

Copper therapy is the most well established means of combating Cryptocaryon irritans (Cardeilhac & Whitaker, 1988). However, copper is lethal to invertebrates, micro fauna and micro flora. Copper is removed from solution by calcium, magnesium and organics.

Copper-based medications (some contain other chemicals in combination with copper) should only be administered in an aquarium that does not contain invertebrates, rock, substrate or other calcareous material.

Copper suppresses immune function and is highly stressful to fish. Copper is also toxic to fish, but to a lesser degree than with invertebrates. Administering a dose that is too high may kill the fish being treated. If the copper level is not high enough then the treatment will be ineffective. This necessitates testing the copper level twice a day and making adjustments as needed.

Take care to read the recommended dosage in the instructions when using any copper-based medication. The correct dosage varies with the product. Test the copper level twice a day with a test kit that will accurately measure the particular type of copper that you are medicating with. The results of using an incorrect dosage with any copper-based medication can be catastrophic. Chelated forms of copper tend to require a higher dose and they are generally less effective than the non-chelated forms. A therapeutic copper level should be maintained continuously for a minimum of three weeks.

I have personally used Cupramine™, a Seachem product, several times with “copper sensitive species” such as lionfish, puffers, dwarf angels and mandarins with impressive results. In my experience, it has been more effective and better tolerated than other forms of copper. Seachem recommends 0.5ppm as the correct dosage for Cupramine. However, I have used this product successfully at 0.4ppm.


Hyposalinity therapy

Hyposalinity therapy has numerous advantages over copper-based medications (Bartelme, 2001c). This method does not suppress immune functions such as phagocytic activity. Antibiotics can be used in conjunction with hyposalinity therapy. Some antibiotics are more effective, or a lower dose is required when the salinity is less than that of natural seawater. The salinity only needs to be checked once a day while administrating treatment. Chemical filters such as carbon and Poly Filter™ can be used when employing hyposalinity therapy.

An accurate means for measuring the salinity is crucial when treating fish with hyposalinity. Swing-arm type hydrometers are notoriously inaccurate. A refractometer, or lab grade, large, glass hydrometer is recommended. Alkalinity and pH tend to fall in diluted saltwater. Check these parameters daily and add a buffer as necessary to maintain the pH between 8.1 and 8.3. Do not expose elasmobranches, invertebrates, live rock, or live sand to treatment with hyposalinity. This method is safe for the bacteria that perform biological filtration, at least if the salinity is not dropped too rapidly. Make two water changes per day for two days, reducing the salinity about 5ppt per water change.

Maintaining the salinity at 16ppt or less has proven to be a highly effective treatment for cryptocaryonosis (Bartelme, 2001a, b). However, this may change with if low salinity variants of Cryptocaryon irritans become common or widespread. The salinity (not to be confused with specific gravity) must be maintained consistently at 16ppt or less for the entire duration of treatment. I suggest 14ppt to allow for any fluctuations in the salinity during therapy while providing some margin for error.

Treatment should continue for a minimum of three weeks after a therapeutic salinity level has been reached. Unlike most other forms of treatment for cryptocaryonosis, hyposalinity does not target the “free-swimming” or theront stage. Hyposalinity therapy works by interrupting the life cycle at the tomont stage. Tomonts are destroyed by hyposaline conditions, thus preventing re-infection.

Teleost reef fish appear to adapt well to hyposaline conditions. Hyposalinity was also reported as an effective treatment for cryptocaryonosis by Angelo Colorni of Israel Oceanographic and Limnological Research Ltd 1985 (Colorni, 1985). A report in Drum and Croaker stated: “We now have experience that proves that a wide variety of teleosts can live quite comfortably at ½ salinity (1.010) for extended periods of up to 2 to 3 months (Goodlett & Ichinotsubo, 1997). Emperor angelfish Pomacanthus imperator were the subjects of one such study. They were kept in salinities as low as 7 ppt for 30 days without any apparent ill effects (Woo & Chung, 1995).


An alternate method of hyposalinity therapy

Treating fish with a series of short-term baths at a salinity of 8 to 10ppt will effectively destroy tomonts. This method requires a three hour treatment every third day for a total of four treatments. All tomonts exposed to a salinity of 10ppt for three hours eventually degenerated (Colorni, 1985). In the event of an infection with a low salinity variant of Cryptocaryon irritans, such as the Chiayi isolate or strain, a salinity of 8 to 10ppt will not effectively eradicate the parasite.

Handling fish every third day that are already weakened by disease may be risky (Colorni, 1985). Teleost reef fish have an internal salinity of 11 to 12ppt. It is questionable as to whether many species of teleost reef fish that can tolerate an external salinity level below that found in their internal fluids without undue stress. Theoretically, the vectors of ionic and osmotic regulatory processes must be reversed as a saltwater fish crosses the line of equal molarity (Evans, 1984). However, recent studies indicate that at least some species of marine teleost fish are capable of adapting to salinities lower than those found in their internal fluids (Woo & Chung, 1995).


Transfer method

The transfer method consists of moving the fish every third day for a total of four moves between two aquariums. The aquariums are then dried between uses to kill the tomonts that are left behind (Noga, 2000. Colorni, 1985). This will effectively interrupt the life cycle of this parasite. Again however, the stress of frequent handling and the potential injuries associated with such a practice could threaten the health and well being of the fish in question (Noga, 2000).


Experimental treatments

The search for new chemicals and methods to control Cryptocaryon irritans continues. The following two treatments are presented as examples and are not intended as a comprehensive list.

The effectiveness of fatty acids against Cryptocaryon irritans was examined using the red sea bream Pagrus major (Hirazawa, et al., 2001). Caprylic acid was found to have the strongest antiparasitic effect. The fish were fed caprylic acid at a rate of 75mg/kg of body weight per day. The results indicated that caprylic acid has an antiparasitic effect against Cryptocaryon irritans, reducing the number trophonts on the fish. However, despite the reduced number of Cryptocaryon irritans, all of the test subjects died as a result of the infection.

The Food and Drug Administration (FDA) has classified hydrogen peroxide as a Low Regulatory Priority (LRP) drug for use in controlling fungus on fish and fish eggs. Hydrogen peroxide has been experimentally proven to be effective against Amyloodinium sp., a marine fish ectoparasite. It was used at a dosage of 25ppm for 30 minutes to treat Pacific Threadfin, Polydactylus sexfilis infected with Amyloodinium ocellatum. (Montgomery et al., 1999b). Some species of fish tolerate the treatment well, but others are highly sensitive to the chemical (Noga, 2000). Results may also vary between juvenile and adult fish.

Hydrogen peroxide is effective against other ectoparasites, such as Ambiphrya and Gyrodactylus spp. (Rach et al. 2000). Sodium percarbonate is a compound that releases hydrogen peroxide when dissolved in water. Sodium percarbonate was demonstrated to kill the freshwater ectoparasite, Ichthyophthirius multifiliis, at the theront stage or free-swimming, infective stage (Buchmann, et al., 2002). It is currently used in Denmark with rainbow trout Oncorhynchus mykiss at a concentration of 50-100 mg/L is twice a week without any apparent ill effects on the fish.

If more than 50% of the theronts died the concentration of hydrogen peroxide was recorded as effective (Buchmann, et al., 2002). A dosage of 12.5mg/L at a temperature of 12°C kills theronts within 3 hours. This same dosage was not effective against the tomocysts stage of Ichthyophthirius multifiliis. However, dosages of 12.5 mg/L for 180 min and 62.5 mg/L for 90 min were effective against theronts (Buchmann, et al., 2002).

The life cycle of Ichthyophthirius multifiliis is temperature dependant, so the warmer the water temperature the shorter the duration of the parasites life cycle. At 12°C, the medium time frame for tomocsyts to hatch is 9 days and the attached parasitic stage has a duration of 10-12 days. This means that at 12°C treatment should continue daily for a minimum of three weeks. Caution should be taken when using hydrogen peroxide as accidental spills may have an immediate adverse effect on human skin.

Studies to test the effectiveness and safety of hydrogen peroxide for the treatment of other ectoparasites such as Cryptocaryon irritans are fully warranted (Montgomery-Brock, D. et al., 2000). However, this treatment is considered to be highly experimental, therefore it cannot be recommended. The side effects and survival rate when using hydrogen peroxide may not prove to be acceptable. Protective clothing and safety glasses should be worn when using a dose of 35% and higher. The water temperature should be carefully monitored when treating with hydrogen peroxide, because it becomes more toxic as the temperature rises. At this point, the safety, effectiveness, correct dosage and duration of treatment for this experimental method have not been established.

To be continued…

The forth installment in this five part series will cover some alternative methods of combating Cryptocaryon irritans. These will include the use of formaldehyde and malachite green, ultra violet sterilizers, freshwater dips, hypersalinity and the sand removal method. Part four will also cover the use of biological cleaners, antimalaria drugs, raising the water temperature, the so-called “reef safe medications and the use of herbal remedies (i.e. garlic) to control Cryptocaryon irritans.



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  2. Bartelme, T.D. “”Cryptocaryon irritans: An Update on the Scourge of Marine Aquariums, Part Two.” Freshwater and Marine Aquarium Magazine, March 2001b.
  3. Bartelme, T. D. “”Treating Saltwater Ich without Medication” Tropical Fish Hobbyist, January 2001c.
  4. Buchmann, K. Jensen, P. B. & Kruse, K. D. “Effects of Sodium Percarbonate and Garlic Extract on Ichthyophthirius multifiliis Theronts and Tomocysts: In Vitro Experiments.” Department of Veterinary Microbiology, Section of Fish Diseases, Royal Veterinary and Agricultural University, Stigbøjlen 4, DK-1870 Frederiksberg C., Denmark, 2002.
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  7. Colorni, A. “Aspects of the Biology of Cryptocaryon irritans and Hyposalinity as a Control Measure in Cultured Gilt-Head Sea Bream Sparus aurata.” Diseases of Aquatic Organisms. 1, 19-22, 1985.
  8. Evans, D.H. “The Roles of Gill Permeability and Transport Mechanisms in Euryhalinity.” Fish Physiology, 10, part B (Hoar, W.S. & Randall, D.J., Eds), pp. 239-283. New York Academic Press. 1984.
  9. Goodlett, R. & Ichinotsubo, L. “Salinity and pH Adjustments for Quarantine Procedures for Marine Teleost Fishes.” Drum and Croaker, 28, 23-26, January 1997.
  10. Hirazawa, N. Oshima, S-I. Hara, T. Mitsuboshi, T. & Hata, K. “”Antiparasitic Effect of Medium-Chain Fatty Acids against the Ciliate Cryptocaryon irritans Infestation in the Red Sea Bream Pagrus major.” Aquaculture, 198(3-4), 219-228, 2001.
  11. Montgomery-Brock, D. Sylvester, J.Y. Tamaru, C. S. & Brock, J. “Hydrogen peroxide treatment for Amyloodinium sp. on mullet ( Mugil cephalus) fry.” Regional Notes, 11(4), Summer 2000.
  12. Montgomery, D., J. Brock and V.T. Sato. “Using hydrogen peroxide for Pacific threadfin infected by Amyloodinium ocellatum.” Regional Notes, 10(2), Winter 1999b.
  13. Noga, E.J. “Fish Disease: Diagnosis and Treatment.” Ames, IA: Iowa State University Press, 2000.
  14. Rach, J.J. Gaikowski, M.P. & Ramsay, R.T. “”Efficacy of Hydrogen Peroxide to Control Parasitic Infestations on Hatchery-Reared Fish.” Journal of Aquatic Animal Health, 12, 267-273, 2000.