Aquarium Fish: News from the Warfront with Cryptocaryon irritans Part Four of Five

by | Feb 15, 2004 | 0 comments

This is the forth installment in a five part series. Part three detailed those few consistently reliable methods or treatments to eradicate Cryptocaryon irritans and some experimental treatments for its control. Part four continues covering some alternative treatments or methods to combat a Cryptocaryon irritans infection.


Alternative Treatments

Many of the purported treatments for cryptocaryonosis are only partially effective at best. Those few treatments that do consistently eradicate this pest still have limitations as to how they may be used. Treatments that utilize copper-based medications or manipulating the salinity are detrimental to invertebrates, micro flora and micro fauna. This makes treating Cryptocaryon irritans infection especially difficult in a reef-type aquarium.

All other known treatments for this disease also have drawbacks. Alternative treatments include but are not limited to formalin, malachite green, ultra violent sterilizers, freshwater dips, hypersalinity, the sand removal method, biological cleaners, herbal remedies, antimalaria drugs, raising the temperature and the so-called “reef-safe” medications. Some alternative treatments or methods can be used in combination with one another. One example would be to add an ultra violent sterilizer to the aquarium while supplementing the diet by soaking the foods with garlic juice or a garlic extract.


Formalin And Malachite

Formaldehyde and Malachite green have been used separately and in combination for the treatment of cryptocaryonosis. These chemicals are toxic to nitrifying bacteria (Cassidy, 1995) and to fish, especially small ones. Both of these chemicals have been demonstrated to elevate blood cortisol levels; therefore, they are immunosuppressive (Donaldson, 1981). Formaldehyde and Malachite green are dangerous to animals and well as humans.

An aqueous solution of 37% to 40% formaldehyde gas equals 100% formalin (Bartelme, 1999). “Formalin is variably successful under aquarium and mariculture conditions” (Herwig, 1978. Moe, 1982. Rasheed, 1989). Formalin is only partially effective because many trophonts are too deeply imbedded to be effected by drugs or chemicals in a dosage that would not kill the host fish. Whether they are used separately or in combination, formalin and malachite green are only partially effective for the treatment of cryptocaryonosis.


Ultra Violet Sterilizers

Ultra violet sterilizers can help prevent the spread of infection between aquariums in a multi-tank system. When an ultra violet sterilizer is placed in the water flow between tanks in a multi-tank system it can eradicate theronts before they can spread into the next aquarium. However, UV lights are less effective at eliminating infection within a single aquarium. Free-swimming theronts can exit tomonts and infect fish before passing through an ultra violet sterilizer. This means that the parasite will continue its cycle life cycle within that aquarium (Gratzek, et al., 1983). Gratzek’s study was performed with freshwater “ick” Ichthyophthirius multifiliis, but it is also believed to apply to Cryptocaryon irritans.


Freshwater Dips

Freshwater dips are largely ineffective in the treatment of Cryptocaryon irritans (Burgess, 1992). The host epidermis and thick layer of mucus form a barrier impervious to osmotic shock (Colorni, 1985). “Most of the trophonts whose hosts had undergone hyposalinity treatment, including freshwater, for at least 18 h, were still alive and occupied the same position in the host by the end of the experiment, following re-adaptation to sea water. They later dropped from the fish, encysted, and the tomonts produced tomites” (Colorni, 1985).

Note that the above quote says “most” and not all trophonts. Trophonts embed themselves completely into the epithelium under a layer of skin. This protects these trophonts from dips. As the trophonts grow in size they gradually displace the overlying epithelium. This is when they become visible as white spots or nodules. Exposed trophonts may be susceptible to freshwater dips, but trophonts that survive continue in their life cycle making this method only partially effective at best.

Freshwater dips can cause osmotic shock. Typically the fish are exposed to the air during the process of capture, handling and transfer, all of which are stressful to the fish. Freshwater dips cannot be depended on as the sole method of treatment for Cryptocaryon irritans and can be counterproductive because they are highly stressful to the fish. They should only be used in combination with other treatments that will successfully interrupt the parasite’s life cycle.



Hypersalinity (salinities higher than natural seawater) has been investigated as a treatment for Cryptocaryonosis. “A salinity of 45ppt was selected because it would likely provide adequate control of the ciliates while minimizing fish stress” (Huff & Burns, 1981). Unfortunately, this method is considered to be more detrimental to the host than the parasite (Colorni, 1985).


Sand Removal Method

The sand removal method consists of removing the substrate every third day for a total of four times. The idea here is to remove tomonts that attach themselves to the sand or substrate before they can hatch (excyst). However, this method is only partially effective, because all of the tomonts are not removed. Tomonts do not attach solely to the sand or substrate. They also form cysts on other hard surfaces in the aquarium such as rock, glass and equipment. Tomonts can also attach to the shells or exoskeletons of invertebrates (Burgess, 1992).


Biological Cleaners

Fish often succumb to cryptocaryonosis despite the presence of biological cleaners such as cleaner shrimp or cleaner wrasse. While cleaners will exhibit their instinctual “cleaning” behaviors, do not assume that they eat trophonts, or eat them in sufficient numbers to affect a cure. “Cleaner” species of fish are also subject to infection.

Alexandra Grutter studied the stomach contents of the common cleaner wrasse or Labroides dimidiatus and found that their diet consists of gnathiid isopods, scales, copepods and non-parasitic copepods (Grutter, 2000). Cryptocaryon irritans was not found in the stomach contents indicating that it is not a part of their diet.


Antimalaria Drugs

Several antimalaria drugs have been used with some degree of success for combating Cryptocaryon irritans. These would include, but are not limited to, chloroquine phosphate, quinine hydrochloride and quinacrine hydrochloride (Atabrine®). A bioassay should be performed before using antimalari drugs, because their strength can vary greatly from one batch to the next.

In my experience, quinicrine hydrochloride was partially effective, but problematic. This treatment caused some of the fish to take on a yellow hue or darken in coloration. It also appeared to cause the fins to begin to fray at about one week into treatment. The recommended treatment period when using quinicrine hydrochloride is 10 days, which is not generally a sufficient period of time to eradicate Cryptocaryon irritans.


Raising The Water Temperature

Temperature manipulation or raising the temperature to 86F is a treatment that has been used with some success against freshwater ick Ichthyophthirius multifiliis. However, the optimal temperature for the reproduction of Cryptocaryon irritans is 86F so raising the temperature to this level will not kill this parasite (Noga, 2000).

Raising the water temperature to a lesser degree has also been suggested as a means of speeding up the life cycle of Cryptocaryon irritans. While it is true that the life cycle of this parasite is temperature dependant, speeding up the life cycle may not be helpful to the fish. Raising the temperature can change the blood pH causing further stress to fish already weakened by disease (Bartelme, 2000a. McDonald & Milligan, 1992). If the water temperature was not too low to begin with, then it may be better not to adjust this parameter. If the temperature is adjusted, any change should be small and take place slowly.


Reef Safe Medications

Despite the product claims of various manufacturers, I have not seen any of the so-called reef safe medication work with consistency for the treatment of Cryptocaryon irritans. When these treatments do appear to work it may be a matter of misdiagnosis or the fish’s own defenses developing partial or full immunity (Burgess, 1992). It is also questionable as to just how safe these treatments are for invertebrates, including those invertebrates that are photosynthetic. In my opinion, using “reef safe” medications can be a waste of precious time when fish are gravely ill. A chemical treatment that is safe, effective and can be used with food fish is still awaited (Colorni & Burgess, 1997).


Herbal Remedies (i.e. Garlic)

Using herbal remedies to combat Cryptocaryon irritans or ich has become more commonplace over the past few years with marine aquarists. Garlic, in particular, has become popular. The foods are soaked daily with garlic prior to feeding the fish for several weeks to combat ich. Unfortunately, evidence to support garlic’s effectiveness or lack thereof, for the treatment of Cryptocaryon irritans is anecdotal (Bartelme, 2003a. Cortes-Jorge, 2000). It seems to work in some cases, especially with light infections, and not in others. However there is some evidence to support garlic as a treatment for some other types of parasites.

An extract of garlic, allium satiyum, has been reported to eradicate trichodinids (Madsen et al. 2000). It has also been demonstrated that garlic extract kills Ichthyophthirius multifiliis, at the theront stage within 15 hours. Ichthyophthirius multifiliis is the freshwater parasite that causes an infection that is often referred to as ick.

The extract was prepared by crushing fresh garlic cloves. The juice was then added to the aquarium at a dosage of 62.5 mg/L to kill theronts.If more than 50% of the theronts died the concentration was recorded as effective ((Buchmann, et al., 2002). A dosage of 570 mg/L was required to kill 100% of the tomocyst stage of Ichthyophthirius multifiliis. Preliminary tests using allium satiyum indicated that it has no effect on trophonts in the skin of fish (Buchmann et al., 2002). The amount of active compounds varies widely among the different varieties of garlic and the use of garlic, by adding it to the water, may prove to be unrealistic ((Buchmann, et al., 2002).

The mechanism of host location for Cryptocaryon irritans is unknown (Colorni & Burgess, 1997). It has been suggested that garlic, when administered orally to fish, may interfere with the parasites ability to parasitize by camouflaging the chemical attraction of fish (Cortes-Jorge, 2000). Chemical attraction requires further investigation (Colorni & Burgess, 1997).


To Be Continued

The fifth and final installment in this five part series will cover the ability of fish to develop full or partial immunity, low salinity variants of Cryptocaryon irritans, the capability of marine teleost fish to adapt to hyposaline conditions and the challenges for improving the transfer method of treatment. It will also cover the difficulties associated with the transfer method, a new or hybrid treatment for Cryptocaryon irritans, four steps to improving this new method of treatment and some tips on how to reduce stress in fish.



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