Amyloodinium ocellatum, more commonly known as Marine Velvet, is one of the most frequently encountered pathogens affecting tropical marine ornamental fishes (Joshi, 2003, Michael, 2002, and Fenner), and also presents a large problem for the food fish industry (Cobb, Levy, & Noga, 1998, Montgomery-Brock et al, 2001, Noga & Levy, 1995, CTSA, Univ. of Florida and Schwarz & Smith). Consequently, a great deal of research has been performed into its control and eradication. Because this scientific research has included the study of the disease's treatments, it is a real windfall for those of us interested in marine ornamentals.

Amyloodinium ocellatum is a dinoflagellate. Think of it as a type of single celled parasitic algae with two flagella that it whips to get around, with characteristics of both plants and animals. Its taxonomical designation is somewhat complex; botanists have preferred to call it an algae and in years past, zoologists have argued it is a protozoan. Amyloodinium are now classed as dinoflagellates in the Kingdom Protista, sort of in between plants an animals being photosynthetic and also motile. At any rate, even though it is no longer classified with protozoans, Amyloodinium ocellatum has a complex lifecycle similar to that of Cryptocaryon irritans (Saltwater Ich), Icthyopthirius multifilis (Freshwater Ich), and species in the genus Piscinoodinium (Freshwater Velvet).

The feeding stage of this parasite is called a trophont. It can be found attached to the infected fish by rhizoids, which are root-like structures that the parasites use to penetrate, hold onto, and feed from their host. Once the trophont matures and grows to an average diameter of approximately 80-100 micrometers (Schwarz & Smith) to a maximum size of 350 micrometers (Noga & Levy, 1995) (for a frame of reference, trophonts of Cryptocaryon irritans have been measured at up to 452 µl (Colorni & Burgess, 1997)), it drops off the host fish, encysts and forms a stage called a tomont. The process of reproductive division then begins. One tomont divides repeatedly until there are up to 256 waiting offspring. It can complete this process rather quickly, in as little as three to five days at water temperatures of 72-77ºF. After these divisions stop, the cyst hatches and releases tiny swarming dinospores, which are as small as 12-15 µl in diameter. In contrast to Cryptocaryon irritans, whose free-swimming theronts are viable for only a day or two, these dinospores remain infective for at least six, and possibly as long as fifteen, days.

Occasionally, a report describes the discovery of Amyloodinium ocellatum tomonts in the stomach, intestines, or esophagus of a fish. I want to be very clear that this does not mean that Marine Velvet has been shown to display a dormant phase, or that it can escape treatment by hiding inside the body of its host. Rather, it is believed that these tomonts developed elsewhere and were merely consumed by the fish afterwards (Noga & Levy, 1995).

Because of its lifecycle, a general recommendation has been to quarantine new acquisitions for 20 days to avoid introducing the disease (Noga, 2000 and Trevor-Jones, 2004), but I would urge most hobbyists to isolate them for a full month, with six weeks being optimal, for a number of reasons. The first reason is for uniformity. Because it will take at least a month to known if your new acquisition is free of Cryptocaryon irritans, it is better to simply get used to a long period of quarantine. Second, the signs of this infection are not obvious and, in my opinion, most aquarists can easily miss them. A full month or more of quarantine should give you enough time to notice the infestation, or, if you don't pick up on the signs, the fish will likely be dead by the end of the quarantine period.

The signs of Marine Velvet infection are rather subtle. Respiratory difficulties seem to be one of the most common signs. Other signs are a decrease or a complete loss of appetite, rubbing against objects in the aquarium, erratic swimming behavior, and a dusty or dull velvety sheen, from which this disease gets its common name. Amyloodinium has shown a preference for first attacking the gill tissue of fish (Noga & Levy, 1995 and Stoskopf, 1993), so once it has spread to the body, I would consider the fish to be heavily infected and perhaps beyond hope of recovery.

Having already written a two-part series on treating Cryptocaryon irritans (Marine Ich), and realizing that it shares many treatments with Amyloodinium ocellatum (Marine Velvet), I won't waste time rehashing what I have already discussed. Instead, I ask you to familiarize yourself with my previous writings on the treatment options for Marine Ich/Cryptocaryon irritans located here and here. This will permit me to delve more deeply into some of the more interesting Amyloodinium ocellatum-specific treatments.

Treatment Option 1: Natural Immunity

As with Cryptocaryon irritans, it has been demonstrated that fish can develop immunity to Amyloodinium ocellatum after several non-lethal exposures, and that this immunity can last for at least six months (Cobb, Levy, & Noga, 1998). In one test, Tomato Clownfish (Amphiprion frenatus) were exposed in containers once per week to 40,000 dinospores per fish for thirty minutes. Afterwards, they were moved to separate aquaria for three days. At that point, each fish was given a freshwater dip for three minutes before being transferred to different recovery aquaria. Each recovery aquarium had its copper concentration maintained at 0.15-0.20 mg/l to cure the infestation. The fish remained there for a week to allow them time to recover. After this, the process was repeated again with another exposure followed by treatment.

After fourteen days a significant number of fish in the experiment showed an immune response, and after twenty-eight days all but one fish in the study were completely free of trophonts. What I found the most interesting was the mode of defense. Immune fish remained susceptible to dinosporic attachment, but for reasons that are unclear, the trophonts never grew, and dropped off their hosts prematurely. It was theorized that the fishes' immune response incorporated an "antitrophont mechanism" by which a host fish that had acquired immunity could "reject trophonts or at least severely retard trophont development." The authors then proposed, as a mode of protection for aquaculture facilities, intentionally adding immune fish to retard the infection of previously unexposed fish. Since both would be susceptible to attachment, the immune fish could be used as a sort of decoy, to decrease the total dinospore count in the environment. This would hopefully subject the non-immune fish to a non-lethal challenge of dinospores, and give those fish more time to develop resistance to the parasite.

The last interesting observation arising from this study concerned immunity specificity. While the authors did not intentionally perform any experiments to test whether this immune response would work only against Amyloodinium ocellatum, they did have an unexpected outbreak of Cryptocaryon irritans, which killed both unexposed and resistant fish. This suggests that any acquired immunity is parasite-specific. This should be a wakeup call to those of you who have still not come around to the necessity of quarantine and preventive treatment. It is better to be safe than sorry, and even professionals with years of training in fish pathology sometimes make mistakes in selecting allegedly healthy fishes. Quarantine, quarantine, quarantine!

While it may appear that natural immunity is the solution to this disease, I would definitely not rely on it. Many times I have read on various message boards that disease problems are related to stress, and therefore if we get rid of the stressors, the fishes' own immune system will take care of the infection. The admonition goes something like, "Feed an excellent diet and maintain optimum water quality, and your problems will go away." My experience has shown, unfortunately, that not taking a quick, proactive stance with treatment will usually doom your fish. In my experience, Amyloodinium ocellatum has always been quick-acting and lethal without early detection and treatment. Waiting for natural immunity to work would be futile, in my opinion. Remember that in the testing the fishes were repeatedly exposed and then cured by using freshwater dips and copper. And, that it was not until after multiple exposures and subsequent treatments that the immunity finally gave the test subjects full protection. Plus, we are talking about parasites here. All the stress in the world cannot make a parasite appear out of thin air. It would be like saying that if you have stress in your life, you will spontaneously develop tapeworms. That does not make sense, and neither does a similar argument regarding fish and their parasites.

Treatment Option 2: Copper

Copper is widely available, inexpensive, and has been proven effective. These attributes have made it the most commonly used chemical treatment for this parasite in the United States (Noga, 2000, Trevor-Jones, 2004, and Univ. of Florida). But, for all its positives, copper can be problematic. It has a narrow range of effectiveness; too high and it can be lethal to the fish, too low and it is useless. It requires daily, or in some instances twice daily, testing and adjustment of the concentration to maintain the appropriate amount, making it a labor-intensive prospect. Still, though, it is cheap, it works, and it can be found in just about any fish store, so it is likely to be the treatment of choice for some time.

Treatment Option 3: Chloroquine diphosphate

Chloroquine diphosphate is a safe and proven effective treatment for Amyloodinium ocellatum. A single dose of 5-10 mg/l will render a fish clean of infestation in ten days (Noga & Levy, 1995). Sounds great, but it too has its drawbacks. First, it is hard to find. I know of only one company that markets this drug for the aquarium industry, Aquatronic's Marex. And while it is reported to be safe for fishes, it is "highly toxic to micro- and macroalgae and to various invertebrates" (Noga & Levy, 1995). So this is yet another effective treatment that, like copper, cannot be administered in a display tank.

Have I mentioned lately the importance of having and using an appropriate quarantine tank? Get one and use it. Poor ATJ, SAT, oama, and the others who are active in the Fish Disease Forum of Reef Central must be going insane answering the daily onslaught of threads there. I know I rarely read the threads there because it is so frustrating and disheartening. They usually go something like this, "I did exactly what every authority in this hobby says not to do. I threw this brand new fish into my tank without a quarantine period. But, he appeared fine to me and I have been keeping marine fish for six whole months now. Plus, the salesperson that sold me the fish assured me that it was healthy and he would not mislead me just to make a buck and get rid of a sick fish. Now all my fish are sick and dying. I don't have a quarantine tank and even if I did I could not possibly catch and remove all my fishes for treatment without tearing apart my whole aquarium. What should I do now? Please help me! I don't want to lose all my fishes!" If quarantine tanks were a standard in this hobby, we would not have nearly as many livestock losses, and subsequently people giving up aquarium keeping every year.

Treatment Option 4: Freshwater Dips

A freshwater dip lasting five minutes has been shown to force the dislodgement of most, although not all, of the trophonts on an infected fish (Noga, 2000 and Noga & Levy, 1995). The problem with freshwater dips is they do nothing about encysted tomonts and swarming dinospores already existing in the infested aquarium. Even if you lucked out and your one freshwater dip was 100% effective, that fish would become infected again upon reintroduction to the infested aquarium.

Even though they are not completely effective, freshwater dips can still be useful. For one thing, they can be used to give an infected fish some immediate comfort by eliminating some of its parasites prior to using another treatment option to affect a complete cure. Also, freshwater dips can be an effective tool for properly diagnosing an Amyloodinium ocellatum infection. A detailed a protocol for properly identifying Marine Velvet using freshwater dips is found here. It is also possible to employ a freshwater dip as a cure in and of itself (Montgomery-Brock et al, 2001). Merely give the infected fish a proper freshwater dip lasting at least five minutes, and then transfer that fish to a new, clean tank. Repeat this procedure every three days, a total of three times. At the end of this course of treatment, the fish should be clear and free of parasites. I have to say that I am reluctant to even mention this protocol. While it can work, it would be extremely stressful to the fish, in my opinion. In this case, I would have to say the cure is almost as bad as the disease. However, that is not too say that I believe freshwater dips are too stressful to be of merit. I do use and recommend freshwater dips as a diagnostic tool as mentioned above and to provide immediate relief to infected fish. I just prefer to not use them repeatedly to affect a cure.

Treatment Option 5: Formalin

Formalin, a solution of formaldehyde gas in water, is a controversial treatment for Amyloodinium ocellatum. Some studies have shown formalin to force the dislodgement of trophonts from test fish, allowing them to be transferred to a clean aquarium free of infestation (Paperna, 1980 and Paperna, 1984). This is similar to the use of freshwater dips and tank transfers in the above treatment option. Formalin at 150 or 200 ppm will cause complete dislodgement in six hours. It will also work at 100 ppm given nine hours of exposure. But, if the fish is administered a formalin bath and then is returned to the same infested aquarium, they will become reinfected readily.

Given a choice between the two, I would prefer freshwater dips. For one thing, you do not have to run out to the local fish store to track down formalin. With a freshwater dip, dechlorinated water and buffer, items that should be readily on hand to any aquarist, are all that are necessary. Plus, formalin is a rather nasty compound. It has been shown to cause cancer in laboratory experiments with rats, and can cause lung damage in humans (Noga, 2000). That is why it is commonly recommended to use formalin only in well-ventilated areas.

Formalin has a rather strange range of effectiveness with regard to the various stages of the lifecycle of Amyloodinium ocellatum. It can force trophonts to drop off their hosts, but does not stop them from forming tomonts. At a concentration of 200 ppm, it can temporarily inhibit division and formation of dinospores, but reproduction will begin again if the formalin is removed. It is, subsequently, not that useful against the encysted tomonts, but effective again against the dinospores once they hatch (Noga, 2000). As an alternative to the bath and transfer method, one could maintain the formalin exposure until all trophonts and tomonts have formed dinospores, but that would require even further exposure of the infected fish and the aquarist to this drug.

Treatment Option 6: Hyposalinity

While hyposalinity is a frequently recommended treatment for Marine Ich/Cryptocaryon irritans, against Marine Velvet/Amyloodinium ocellatum it is unlikely to be useful. Amyloodinium ocellatum can survive a much wider range of environments than can Cryptocaryon irritans. A salinity of 16 ppt for 28 days is usually recommended to kill Cryptocaryon irritans (Noga, 2000), but Amyloodinium ocellatum has been found in salinities ranging from 3 to 45 ppt (Noga, 2000), with its optimum range of salinity for reproduction at 16.7 to 28.5 ppt (Univ. of Florida). Clearly, lowering the salinity is not going to be effective.

I want to leave the reader with one short note on the use of hyposalinity for combating Cryptocaryon irritans before I continue. Hyposalinity has been extremely effective against Cryptocaryon irritans and likely will continue to be for some time. But, recent research has suggested that the salinity range of that parasite has expanded. I would suggest reading Terry Bartelme's article here regarding the adaptability of the parasite Cryptocaryon irritans in certain locales.

Treatment Option 7: Acriflavin, Aminoacridine, and Formalin Combination Therapy

This is one of the more recent medications to enter the marketplace. Its claim to fame is that it is allegedly a reef-safe alternative. In fact, the label on the back of the bottle uses the term "reef safe" and then goes on to state, "Safe for all fish (including scaleless fish), plants, corals, and invertebrates. Will not affect biofiltration." The active ingredients are listed as acriflavine, aminoacridine, and formalin. Let's discuss these in order.

Acriflavin does work against some bacterial, fungal, and parasitic infections (Noga, 2000). I even found reference to Acriflavin at a concentration of 6 ppm working against reproduction in tomonts (Paperna, 1984). That is the plus side. The downside is it is reportedly not as effective as other agents against any kind of infection, be it bacterial, fungal, or parasitic (Noga, 2000). It also discolors the water, which is particularly problematic in a reef tank with photosynthetic organisms requiring light to produce energy, and it can be toxic to some fish (Gratzek et al, 1992). Its potential toxicity to some fish does not bode well for its use in a complex ecosystem such as a mature reef aquarium. Along with that, its broad-spectrum nature (i.e., it can kill some bacteria, fungi, and parasites) concerns me with its use in a reef display.

I was unable to find much information regarding treating fish disease with Aminoacridine. It was one of the ingredients of Tetra's now discontinued Oomed, which was claimed to work against Amyloodinium ocellatum. Other than that, I found a lot of disturbing information in various scientific papers concerning the use of this drug as a mutagen (Medical Dictionary Online and SCIRUS). Furthermore, in talks with Anthony Calfo about Oomed, he recalled some concern when Oomed was available regarding its Aminoacridine component. He related to me the apprehension that was expressed to him, in a fish pathology course for aquarists at the University of Georgia, about Aminoacridine potentially lowering a fishes' chance of reproductive success. This was specifically with regard to the commercial breeding of freshwater Angelfish and Discus (Pterophyllum scalare and Symphysodon species respectively), so I am unsure how it would relate to saltwater fishes and invertebrates, but it is something that should give you pause.

Last is the formalin factor. In treatment option 4 I discussed formalin's limited effectiveness against Amyloodinium ocellatum. Formalin is, however, reported to be toxic to algae and macrophytes/plants (Noga, 2000), which in my mind definitely brings into question its use in a reef tank.

Before I would feel comfortable using this combination therapy in my reef, I would need to see documented proof of its effectiveness against Amyloodinium ocellatum and, more importantly, toxicology test results ensuring that it was safe for the inhabitants of my aquarium. I was unable to find either. If anyone knows of any data, please feel free to post in my author's forum. I would be pleased to see it. Until such time, I know I will not be using it.

Treatment Option 8: Ascorbic Acid

This is yet another medication which claims to be a reef-safe cure for Marine Velvet. The packaging states (Please bear with me as the manufacturer has a rather poor translation from German to English and is still using the old name of Oodinium for this parasite), "Eliminates for oodinium in salt water. Safe with invertebrates and algae. For best results complete the treatment program. Remove carbon and other chemical filters. Mechanically filter over floss or a sponge. Do not use ozone or UV sterilizers or protein skimmer. Nitrifying bacteria will not be harmed but will be repressed. After treatment undertake a partial water change and use Axxxxxxx Bxxxxx to re-invigorate the nitrifying bacteria." The bottle also labels the active ingredient as ascorbic acid. If you don't know what ascorbic acid is, perhaps you may have heard of it by a more common name, Vitamin C. I was unable to find any reference to using ascorbic acid or Vitamin C to combat Amyloodinium ocellatum in any of the articles or fish texts that I have read. In the absence of documented, scientific studies confirming the effectiveness of this treatment, I am leery of recommending its use. It is possible that I missed some study confirming its validity, so if anyone knows of one, let me know in my author's forum. Until such time, I cannot recommend its use.

Treatment Option 9: Ultraviolet Sterilization

Ultraviolet radiation can kill the infectious, free-swimming dinospores of Amyloodinium ocellatum (Noga, 2000), but its use as a cure here has the same drawbacks as when used against Cryptocaryon irritans. Please see here for that discussion if you so desire. Suffice it to say that UV devices can be useful in controlling the spread of disease from tank to tank in commercial settings that use a central filtration system, but are unlikely to affect a cure or even control the spread of the parasites from fish to fish in a display aquarium.

Treatment Option 10: Ozone

I don't have a lot to say about ozone. It is similar to UV, as most people who use it for disease cure and prevention, are using it as a sterilizer. In my opinion, however, it maybe slightly more effective than a UV sterilizer because ozone does not present as many maintenance issues as UV sterilizers do, such as the decreasing effectiveness seen as the UV lamp ages, or as a film develops on the quartz sleeve and blocks the UV light from penetrating and treating the water flowing through the unit. With an ozone generator teamed to an ORP monitor or controller, the user will be able to track the effectiveness of the ozone. Suffice to say, ozone can be employed to control the spread of the disease from aquarium to aquarium on a central filtration system, but I would not count on it to affect a cure in a display tank.

Treatment Option 11: Biological Controls

While it is a commonly held belief in aquarium circles that various cleaner organisms, namely Labroides wrasses, Elacatinus (formerly Gobiosoma) gobies, and Lysmata shrimp, can help cure diseases such as Cryptocaryon irritans and Amyloodinium ocellatum, that belief is unfounded. Though I discussed this in more detail in my articles on treating Marine Ich, I will state the highlights again here. Neither Cryptocaryon irritans nor Amyloodinium ocellatum is routinely found in the wild, and it stands to reason that no cleaner organism would evolve to feed on a parasite that was rarely available. Plus, it has been shown that Elacatinus gobies and Labroides wrasses feed almost exclusively on gnathid isopods in the wild, so the chances of them being useful in combating common aquarium pathogens is unlikely. Also, cleaner fishes are just as susceptible to infection as are the fish they are alleged to be helping. One of the first signs of an infected fish is loss of appetite, which would render sick cleaners useless.

Treatment Option 12: Hydrogen Peroxide

This is one of the newest ideas for treating Amyloodinium ocellatum and, in my mind, one of the most interesting and promising as well. The first study used 20 juvenile Pacific Threadfin (Polydactylus sexfilis) suffering with an infection of Amyloodinium ocellatum. They were randomly divided into four open water tanks. One tank was the control and received no treatment. The control fish were examined and found to have a mean of 16.6 ± 16.2 trophonts per gill biopsy. The fish that were to be treated with varying levels of hydrogen peroxide were also examined and found to harbor a mean of 35.6 ± 38.7 trophonts per gill biopsy. Water flow to the three treatment tanks was stopped and they were dosed with hydrogen peroxide at concentrations of 75, 150, and 300 ppm. The fish were exposed for thirty minutes and then the water flow was returned to rid the tanks of the hydrogen peroxide. Within one hour of treatment, all the fish exposed to 300 ppm hydrogen peroxide had perished, but the fish exposed to only 75 and 150 ppm tolerated the treatment without any deaths. The surviving fish were examined immediately after treatment and found to harbor no more parasites. They were re-examined the following day. The treated fish were still infection free while the untreated fish were found to have an increase in the trophonts counted.

Another test was set up at the facility where the sick fish were obtained. Scientists used a grow out tank that contained fish infected at a rate of 16.3 ± 13.0 trophonts per gill biopsy. These fish were exposed to 75 ppm hydrogen peroxide for thirty minutes. One day after exposure, the trophonts' count dropped to 4.7 ± 0.6. After six days, the count was down to 1.0 ± 1.0. At this point, the fish were retreated with 75 ppm hydrogen peroxide for another thirty minutes. The day after the second treatment, no trophonts could be found. Because the study's participants were unsure of the effect of hydrogen peroxide against tomonts, they transferred the fish to a clean tank at this time.

Some of these same people then prepared an experiment on Mullet (Mugil cephalus) fry. They first studied hydrogen peroxide's effect on healthy fish. Three groups of ten healthy fish were exposed to 75, 50, and 25 ppm hydrogen peroxide for thirty minutes. After 24 hours, the survival rates were 20, 50, and 70% respectively. They then decided to test 25 ppm hydrogen peroxide on a large larvae-rearing tank. This tank held 3000 liters of water and approximately three fish per liter. The facility had been experiencing 200-1000 deaths per day from Amyloodinium ocellatum for one week prior to the test in this vessel, while the standard daily mortality should have been 0.002%. The fish were treated for 30 minutes with 25 ppm hydrogen peroxide. Within three days of the exposure, mortality dropped to less than 10 per day.

Now before you all go running off to the medicine cabinet, please remember that this treatment is experimental at best. It can easily be overdosed and cause mass mortalities. I would wait until further research has been performed to test the tolerance of various marine ornamentals to hydrogen peroxide exposure. Just to be clear, I am not currently recommending the use of hydrogen peroxide. If you choose to experiment and use it, you could very well be risking the lives of every inhabitant in your aquarium. I mention it only because it is promising, and as something to keep an eye out for in the future, after additional testing has been done. If you wipe out your aquarium with this treatment, don't come crying to me later.

Treatment Option 13: Flushing and Near Darkness

Flushing is a term used to describe a procedure utilized in the aquaculture of food fish when a parasitic disease strikes an open water system. It is simply the effort to turnover the tank's water fast enough to interrupt the lifecycle of the parasites. Put another way, they try to blow the parasites out to sea while not attached to the fish. This strategy is moderately successful at best. The reasons are quite simple. The number of free-swimming dinospores in the water column is diluted with each water exchange, but they are just that, diluted. There are still enough of them of continue to infect and reproduce. Additionally, even as they are being diluted, they continue to reproduce and multiply. You may think this could be remedied with a higher turnover rate, but it remains impossible to change 100% of the water (and dinospores) in this manner. Escobal's "Aquatic System Engineering" gives an excellent explanation of the reasoning behind this if you wish to view the math behind this statement.

So, why is this method used in the first place? Well for one, it is convenient and easy. Fresh seawater is already being pumped in to maintain water quality; merely increasing the rate of exchange to try to flush out parasites is a simple matter of turning up the pumps. Also, attempting a chemotherapeutic treatment would be difficult with an open system because of the constant dilution of the chemical agent.

So, is this method likely to be a total failure? No, not really. Some research has suggested modifying this technique for greater success, and this is the real reason I wanted to discuss it (Montgomery-Brock & Brock, 2001). In experiments with Pacific Threadfin in Hawaii, scientists tried the flushing technique, but with one change: covering the fish raceways to reduce the light level to near total darkness. The idea behind this was that the low light conditions would be unfavorable to algae. This in turn would rob the tomonts of an appropriate substrate to adhere to, leaving them with nothing to grasp but the bare walls of the raceways, thereby facilitating flushing them out to sea.

The first test used 26 mildly infected fish obtained from a fish farm experiencing difficulties with Amyloodinium ocellatum. These subjects were divided into two equal groups. The fish kept exposed to sunlight showed an increase in trophont counts, while the fish kept in the dark saw their counts decrease. After this trial, the farm with the troubles covered several of its raceways and those too had a dramatic decrease in mortalities compared to lit vessels. Subsequently, this farm covered all its livestock and has operated for over one year since without an outbreak of Amyloodinium ocellatum.

The reason I wanted to relate this story is to expand upon an idea I advocated in my first article on Cryptocaryon irritans, with regard to quarantining livestock. I prefer to use bare bottom tanks and daily water changes for all new fish upon their first arrival. This eases cleaning, but was also shown to be inhospitable to the tomonts of Cryptocaryon irritans. The research above lends additional strength to the argument for employing an unnatural environment, such as a bare bottom glass aquarium, for quarantine to decrease the likelihood of disease. This also runs counter to the belief that the supposed magical healing properties of a beautiful, healthy, natural display tank can cure even a suspect fish. In reality, such a tank really offers the parasites a near perfect place to reproduce; plenty of appropriate substrate to adhere to and a plethora of potential hosts confined in a relatively small body of water.

While some people point to the sheer number of filter feeding organisms in a mature reef display and argue that they are very efficient and effective predators on a wide variety of plankton, which would include the intermediate, free-swimming stages of fish parasites, experience has shown time and time again that this is not a reliable solution. While bringing home a suspect animal and placing it in an otherwise healthy aquarium works sometimes, it is just as likely to not work and infect the entire tank. I would argue that in many of the instances where this appears to work, that it is just as possible that the sick fish has been exposed and cured of the parasite numerous times during the chain of custody. In commercial settings with a constant influx of new animals, it is routine to have outbreaks that need to be dealt with. If this happens several times to a particular fish while making its way from the reef to your reef, it would eventually build up immunity. It is quite likely that some of these hobbyists reporting a sick fish coming around after being added to their display are nothing more than instances where natural acquired immunity has finally kicked in. In this scenario, the health, or lack thereof, of the final holding vessel would be irrelevant. It would merely be a matter of time, exposure, and treatments by someone else that saved the fish and not the expertise of the hobbyist or the overall health of their display.

Note that while Amyloodinium ocellatum is a dinoflagellate, related to algae, the researchers concluded that the parasites were incapable of photosynthesis and that the lack of sunlight did not have any direct effect on the parasite (Montgomery-Brock pers. comm.).


Hopefully, I have sufficiently covered the treatment options available for dealing with this parasite. I strongly urge aquarists to take a proactive stance. Be strict and quarantine all new additions for at least one month, preferably longer. Keep a close eye out for the subtle signs of this infection. And lastly, be prepared to act quickly with a proven treatment if the presence of this pathogen is suspected in your tank. At this time, only copper and chloroquine diphosphate have been proven effective and safe sufficiently for me to use and recommend. I am hopeful hydrogen peroxide will be further studied, as I believe it has the most potential for a reef-safe treatment option, but additional experimentation is needed.


I'd like to take a moment to thank Anthony Calfo, Robert Fenner, Dr. Ron Shimek, and Andrew Trevor-Jones for their editorial advice and content.

If you have any questions about this article, please visit my author forum on Reef Central.


Bartelme, Terry. 2003. "News from the Warfront with Cryptocaryon irritans, Part Two of Five" Advanced Aquarist, December 2003.

Bassleer, Gerald. 1996. Diseases in Marine Aquarium Fish: Causes, Symptoms, Treatment. Westmeerbeek, Belgium: Bassleer Biofish.

Calfo, Anthony. pers. comm.

Cobb, Charles S., Michael G. Levy, & Edward J. Noga. 1998. "Development of Immunity by the Tomato Clownfish Amphiprion frenatus to the Dinoflagellate Parasite Amyloodinium ocellatum" Journal of Aquatic Animal Health, vol. 10 no. 3 pp. 259-263, 1998.

Colorni, Angelo and Peter Burgess. 1997. "Cryptocaryon irritans Brown 1952, the cause of 'white spot disease' in marine fish: an update" Aquarium Sciences and Conservation, 1:217-238, 1997.

Escobal, P. R. 1996. Aquatic Systems Engineering: Devices And How They Function. Oxnard, CA: Dimension Engineering Press.

Gratzek, Dr. John B., Dr. Richard E. Wolke, Dr. Emmett B. Shotts Jr., Dr. Donald Dawe, and George C. Blasiola. 1992. Aquariology: Fish Diseases & Water Chemistry. Blacksburg, VA: Tetra Press.

Joshi, Sanjay. 2003. "Top 5 Marine Fish Parasites" Aquarium Fish Magazine, September 2003.

Michael, Scott. 2002. "Fighting Marine Parasites" Aquarium Fish Magazine, October 2002.

Montgomery-Brock, Dee & James A Brock. 2001. "The Utilization of Low Light Conditions as a Means for Controlling Amyloodinium sp. Disease on the Pacific Threadfin, Polydactylus sexifilis" Aquaculture-2001: Book of Abstracts, page 450.

Montgomery-Brock, Dee, Vernon T Sato, James A Brock, & Clyde S. Tamaru. 2001. "The Application of Hydrogen Peroxide as a Treatment for the Ectoparasite Amyloodinium ocellatum (Brown 1931) on the Pacific Threadfin Polydactylus sexifilis" Journal of the World Aquaculture Society, vol. 32, no. 2, pp. 250-254, June 2001.

Montgomery-Brock, Dee. pers. comm.

Noga, Edward J. 2000. Fish Disease: Diagnosis and Treatment. Ames, IA: Iowa State University Press.

Noga E.J. and Levy M.G. 1995. Dinoflagellida (Phylum Sarcomastigophora) In: P. T. K. Woo (ed.) Fish Diseases and Disorders. Volume 1: Protozoan and Metazoan Infections. Wallingford, Oxon, United Kingdom: CAB International. pages 1-25.

Paperna, Ilan. 1980. "Amyloodinium ocellatum (Brown, 1931) (Dinoflagellida) infestations in cultured marine fish at Eiliat, Red Sea: epizootiology and pathology" Journal of Fish Diseases 3:363-372, 1980.

Paperna, Ilan. 1984. "Chemical control of Amyloodinium ocellatum (Brown, 1931) (Dinoflagellida) infections: in vitro tests and treatment trials with infected fishes" Aquaculture 38:1-18, 1984.

Shimek, Dr. Ronald. pers. comm.

Stoskopf, Michael. 1993. Fish Medicine. Philadelphia, PA: W. B. Saunders Company, page 647.

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