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Related Articles: Marine Ich, Cryptocaryoniasis, Marine Parasitic DiseaseFreshwater IchQuarantine, Quarantine of Marine Fishes

Marine Ich: Fighting The War On Two Fronts

By Scott Fellman ScottF@wetwebmedia.com

As the marine hobby grows, new techniques, procedures, and technology have made the husbandry of fishes, invertebrates, and other organisms easier and easier. However, there is still one dreaded scourge which occasionally attacks our prized fishes: Marine Ich. This disease is probably the most common affliction that most hobbyists will encounter. Although ich is such a common problem, there are probably as many different approaches to treating it as there are hobbyists! The focus of this article, however, will be on what I call a "two front" approach to attacking ich. An approach that, although not new, and by no means revolutionary- has a very high success rate. Although there are a number of alternative therapies that have been used to treat this disease, there are very few, in my opinion, that are as effective (and successful!) as the approach that we will discuss here. Let's begin with a quick review of what causes ich, the symptoms of the illness, and a look at the life cycle of the parasite that causes this dreaded affliction. By understanding the life cycle of the parasite, we can develop an effective strategy to defeat the disease.

The ugly little causative parasite of Marine Ich is the ciliated protozoan, Cryptocaryon irritans (even the name sounds bad!). The parasite has a rather simple life cycle, and has several different phases during its life cycle when it is especially vulnerable. The parasite, in its free swimming phase, locates a suitable host (i.e.; your fishes!), and burrows into the host's skin, gills, and fins, where it feeds on the fluids contained within the host's body. For protection, the parasites form a thin cyst over themselves. The cysts, which look a lot like grains of salt, are usually the aquarist's first signal that the fish has contracted the disease. The encysted parasites, called trophonts, remain attached to their fish host for approximately 7 days until the protozoan reaches maturity. Next, the protozoan leaves the host and enters the water column as single cell, known as a tomont. The tomont (or cyst) can swim for up to 18 hours before it attaches to a suitable substrate, such as sand, rock, or the aquarium itself. Then, the cells within the cysts divide, and form up to 200 "daughter" parasites, or tomites. This process, which takes anywhere from 4 to 28 days, results in a new generation of free swimming protozoans called theronts. The theronts must then locate and inhabit a suitable host to complete their life cycle within several hours, or they will die. It is during this free swimming phase that the Cryptocaryon parasite is most vulnerable, and this is the part of the life cycle when Marine Ich can be eradicated with a relatively high degree of success.

The "Two Front" Approach To Ich Treatment

My approach to defeating marine ich consists of battling the illness on two "fronts": The "home front" (the main aquarium), and the "battle front" (the treatment aquarium). Attacking ich in the main system is a relatively simple processes, and requires little more than patience and perseverance. The attack on the "battle front" requires the use of readily available medications. Let's look at what to do once ich manifests itself in your aquarium.

Recognizing The Symptoms of Marine Ich

Usually, the first signs that a fish is infected with ich manifest themselves shortly after the parasites lodge themselves in your fishes' skin, gills, and fins. Affected fishes will usually show small (up to 1mm) white spots throughout their bodies, which look very similar to grains of salt. The fishes will often be seen attempting to scratch themselves against rocks , corals, the substrate, or other aquarium d?or, in an attempt to relieve themselves of the discomfort. If left untreated, the parasites can attach themselves into the fishes' gill tissues to the point where they can interfere with the fishes' respiration. Obviously, the aquarist is advised to take action as soon as possible to save the lives of his or her fishes.

After you have confirmed that you are, indeed dealing with Marine Ich , your first move in attacking this disease is to remove all of the fishes from the affected aquarium to a separate, bare aquarium of appropriate size for a treatment and recovery regimen that will last from 30 to 45 days. Did I just say "all of the fishes", even if they are not showing signs of infection? Yes I did! Even though they may not be displaying symptoms now, they have been exposed, and the very real possibility of infection looms. If there is one thing I have learned in my battles with this disease, it is that it's always better to be safe then sorry! The first half of the treatment period will involve treating the fishes with medication, and the second half of the treatment period will allow the fishes to regain their strength before being returned to their aquarium. By following this careful treatment regimen, you will assure that your fishes have their best chance to recover from this nasty disease.

I highly recommend performing a freshwater dip on each fish before being placed in the treatment tank. The freshwater should be properly buffered and heated to the same temperature as the tank that your fishes have been residing in. Use of a non-toxic anti-bacterial agent, such as Methylene Blue, is encouraged during the dip. Use enough Methylene Blue to color the water a deep blue. The duration of the dip should be from 3 to 5 minutes, depending on the tolerance of the individual fish(es) being dipped. Keep a close eye on the fish during the dip process, and be prepared to remove them to the treatment tank quickly, should they show extreme distress during this process. The freshwater dip is a standard part of the acclimation and quarantine process at most public aquariums throughout the world, and is an effective procedure that can reduce or eliminate many external parasites, including Cryptocaryon. The reason that freshwater dips are so successful is that the parasites simply cannot make the osmotic "stretch" to freshwater as well as the fish can.

After the dip process has been completed, the fishes should be placed in the treatment aquarium. The aquarium should have water conditions (specific gravity, pH, etc) that approximate those in the aquarium from which they came. Some hobbyists prefer to lower the specific gravity in the treatment aquarium to 1.015 or less, a procedure known as "hyposalinity". This technique is used for many of the same reasons that the freshwater dip is performed. I personally do not utilize this process, but it certainly has its proponents.

Administer an over-the-counter copper sulphate preparation (specifically formulated for aquarium use). Follow the manufacturer's instructions concerning its use exactly as instructed by the manufacturer. Always use a test kit to monitor the concentration of copper in the water, in order to assure that you're maintaining a proper therapeutic dosage. Be sure that you replenish the copper as needed each time you change the water in the treatment aquarium. Do not assume that your treatment tank has the correct level of copper! You run the risk of diluting the copper to an ineffective level, or possibly increasing it to a toxic level. I cannot stress it enough-always test the copper level when using it to treat disease. It literally could mean the difference between life or death for your fishes. Enough said.

Since the Cryptocaryon parasite enters a free-swimming phase, when it heads to the bottom of the aquarium after detaching from the fishes, you may actually be removing some of these parasite cysts when you siphon debris from the bottom of the treatment aquarium. Regular water changes are a highly effective means of maintaining water quality and removing some of these cysts. I recommend changing 5% of the treatment aquarium's water volume twice a week during the treatment period.

Long-term exposure to copper can be harmful to fishes. Tangs, in particular, can suffer if they linger too long in copper-treated water. They harbor beneficial digestive bacteria, which enable them to process their food. These bacteria may be adversely affected by long-term copper exposure. The idea here is to employ a one-to-two-week exposure to the copper medication, and then reduce the copper level through water changes (without replenishing the copper, of course) and absorptive filter media, such as Poly Filter. If you are treating fishes such as Centropyge angelfishes, which have a reputation for copper sensitivity, you may want to utilize an aquarium medication containing Formalin, instead of copper. The remainder of your fishes stay in the treatment aquarium will be dedicated to providing them with high-quality foods, good water quality, and careful observation. Use this period of time to ascertain that your fishes are once again healthy, and that no secondary infections have had the opportunity to manifest themselves.

The Home Front

After removing your fishes to a "hospital" tank for observation and treatment, you will have created a serious disruption to the life cycle of the Cryptocaryon parasite. Your main system will be running in a "fallow" state. Invertebrates may remain in the display aquarium, as they are not susceptible to the illness, nor are they thought to be a "vector" for the illness. In the absence of hosts, most of the free-swimming theronts will perish . This is where an understanding of the parasite's life cycle will pay off. By letting your tank run "fallow", you will significantly reduce the number of parasites remaining in the system, which will make the likelihood of a new outbreak much less when your fishes are "repatriated".

The fallow period will last a minimum of one month. During the fallow period, do continue to perform routine water changes and other maintenance tasks in the aquarium. Not only will you be maintaining a cleaner system with fewer organics, but you may actually be physically removing some of the encysted and free-swimming parasites themselves from the system, particularly if you siphon the substrate. Also, performing your routine maintenance procedures on your tank during the fallow period, you help assure that your newly-cured specimens will be returning to a clean, stable aquarium environment.

After the fallow period, and after you have determined that your fishes are once again in good health, you may return them back to their aquarium. The procedure that I have outlined here is based upon successful, tried-and-true methods used by countless private and professional aquarists alike for years. None of the procedures are radical or revolutionary, but they do work! Keep in mind, however, that no treatment procedure, regardless of how well thought out or comprehensive, can guarantee 100% effectiveness at eradicating this, or any disease. As more research is done in the marine fish arena, no doubt more comprehensive and effective treatment protocols may enter the fray.

There are a few promising alternative treatment techniques for ich that are being discussed with increasing frequency on marine hobby internet message boards and in hobby publications. The use of garlic extract to treat marine ich has received quite a bit of attention lately, although its effectiveness is based largely on anecdotal evidence, and has not been thoroughly studied to date. Garlic proponents suggest that a substance contained in fresh garlic extract, Allicin (Diallyl thiosulphate) acts as a "blocker" to chemical cues used by the Cryptocaryon parasite to recognize its potential host. Use of garlic extracts may prove to be more valuable as a preventative, rather than a true "treatment" after the disease has manifested itself in fishes. Hopefully, further research at both the hobby and scientific level will yield further useful answers on this topic.


While we're on the subject of prevention, possibly one of the most effective means of ich prevention is the regular use of a quarantine period for all new fishes, before they are placed in the main aquarium. A three to four week quarantine gives the aquarist tremendous control, and allows the aquarist the opportunity to observe his or her specimens without fear of transmitting possible illnesses to the inhabitants of the main aquarium. Since many parasitic diseases, including ich, manifest themselves after a few weeks, it simply doesn't make sense to not quarantine your fishes. Proper use of quarantine procedures will make a huge difference in your success as an aquarist.

After initial quarantine of your newly-received fishes, the best thing that you can do to prevent ich and other diseases from taking over your aquarium is to provide a proper, stable environment for your animals. Methods to achieve this include careful, sparse stocking of animals, proper diet, and a regular, comprehensive maintenance and testing regimen.

Rather than striving for a specific "number" on a test kit, the aquarist should endeavor to maintain stability. This means that if your tank temperature is 79 degrees Fahrenheit, you should do all that you can to maintain that temperature on a consistent basis. If your system runs at a specific gravity of 1.025, utilize top offs and regular water changes to keep it that specific gravity. As you are no doubt aware, the ocean is among the most stable environments on earth, and most fishes have not evolved to tolerate rapid environmental changes without incurring severe stress. And continuous stress can lead to disease!

While we're on the subject of stress, it goes without saying that few things contribute to greater stress in captive marine fishes than an overcrowded, inappropriate mix of animals. For example, maintaining small, docile fishes, such as Mandarins or Anthias with aggressive, territorial, or fast-moving fishes such as Damselfishes, Triggerfishes, and Groupers, is a recipe for disaster in the confines of an aquarium. A fish that is subjected to harassment from its tankmates will constantly hide, fail to eat properly, and generally decline in health quite rapidly. The same goes for fishes that require large amounts of space, such as tangs. When confined to an aquarium that is too small, these fishes will display very "unnatural" behaviors, such as "hyper aggression", hiding or sulking, or failure to engage in feeding behavior, which will, of course, lead to stress. Conscientious aquarists will always implement a stocking plan for their aquarium that makes sense for the animals to be kept, and takes into account the size of the tank, not to mention the ability of the aquarist to provide for the animal's needs. A little advance planning can pay big dividends down the line for future aquarium inhabitants.


Marine Ich is certainly a dreaded disease; one that most aquarists may have to contend with at some point during their hobby "career". As frustrating as this disease may be to deal with, I hope that the strategy outlined in this article provides you with the encouragement you will need to attack it-and win! When you are battling this illness, one of the most important things that you need to have is a measure of patience! Since we are talking about a treatment protocol that lasts a month or more, you need to "stick it out" and stay with the program. As we have discussed, this treatment only works if the aquarium is left fallow for a sufficient duration to affect a cure. As with many worthwhile endeavors, the successful treatment of this disease will take time, so remind yourself over and over again that the goal can be achieved, and that you will be successful. Good luck!



Cortes-Jorge, Jr., Horge Garlic Versus Marine Ich. www.reefs.org 2000

Fenner, Robert M. 1998. The Conscientious Marine Aquarist. Microcosm, Ltd. Shelbourne, Vermont

Post, George 1987. Textbook of Fish Health. Tropical Fish Hobbyist Publications Neptune City, New Jersey

Tullock, John H. 1997. Natural Reef Aquariums. Microcosm, Ltd. Shelbourne Vermont

Steven Pro's excellent ich articles that start here: http://reefkeeping.com/issues/2003-08/sp/index.htm & Terry Bartelme's http://www.advancedaquarist.com/issues/nov2003/mini1.htm http://www.advancedaquarist.com/issues/dec2003/mini2.htm http://www.advancedaquarist.com/issues/jan2004/mini3.htm http://www.advancedaquarist.com/issues/feb2004/mini4.htm http://www.advancedaquarist.com/issues/mar2004/mini5.htm

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