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cryptocaryon irritans (marine ich) Part I

Posted 12/18/2010 at 10:01 AM by snorvich
Updated 03/03/2014 at 09:58 AM by snorvich

The life cycle of this parasite is interesting and is important to understand when evaluating a treatment. The stage where the parasite is attached to a fish is called a trophont. The trophont will spend three to seven days (depending on temperature) feeding on the fish and that is what you see symptomatically when you see "salt sprinkled on the fish". However ich does not have to be visible in order to be present. After that, the trophont leaves the fish and becomes what is called a protomont. This protomont travels to the substrate and begins to crawl around for usually two to eight hours, but it could go for as long as eighteen hours after it leaves it's fish host. Once the protomont attaches to a surface, it begins to encyst and is now called a tomont. Division inside the cyst into hundreds of daughter parasites, called tomites, begins shortly thereafter. This noninfectious stage can last anywhere from three to twenty-eight days. During this extended period, the parasite cyst is lying in wait for a host. After this period, the tomites hatch and begin swimming around, looking for a fish host. At this point, they are called theronts, and they must find a host within twenty-four hours or die. They prefer to seek out the skin and gill tissue, then transform into trophonts, and begin the process all over again. What this means is that when your tank is infected, you can actually see symptoms during a very small part of the life cycle, and it why your tank is infected even though your fish may be resistant. It will also explain why symptoms come and go. Note however, that resistant fish can still be carriers of the parasite

Many hobbyists are fooled into believing they have cured their fish of the parasites, only to find Ich present again on fish a few weeks later; a reason why following through with a full treatment protocol is so important. Don't make this mistake and be lulled into a false sense of security. The parasites may be in a stage where they are merely regrouping and multiplying for their "next offensive." In the wild, this sort of massive reproductive phase ensures that a few will find a suitable host to continue on the cycle. In the close confines of our aquariums, though, it means comparatively massive infection rates. It also suggests that smaller tanks, where reinfection will be more severe due to tomite density, will cause the parasite to overwhelm fish quicker than in larger tanks.

This disease is usually associated with several environmental triggers. Changes in water temperature, exposure to high levels of ammonia, nitrite, or nitrate, low pH levels, low dissolved oxygen often associated with overcrowding, are all factors contributing to the onset of the disease. However, unless ich is present in the tank, your fish cannot be infected. You could lump all of these in a general category of "stress", but it is more appropriate to think of all of these as "unnatural conditions". In fact, Cryptocaryon irritans is rare in the wild and even more unlikely to be lethal. Since fish in the wild move around on a day to day basis, infection is a low probability event. Ich is truly a disease that exploits the conditions of captivity to reproduce and easily find suitable hosts.

By the way, trophonts are under the skin so cleaner wrasses, cleaner gobies, and cleaner shrimp have no real effect on reducing this parasite.

Treatments for Marine Ich (MI) or cryptocaryon irritans:

1. Hyposalinity - Using a refractometer, hold salinity at 11ppt to 12ppt until 4 weeks after the last spot was seen. (Best to use salinity, but if you use specific gravity, that equates to roughly 1.008 to 1.009 sp. gr. units). Raise salinity slowly and observe fish for 4 more weeks. Hard to control pH and water quality during treatment. This is the most difficult to execute treatment for the fish because evaporation can change Specific Gravity of the water and because properly calibrated refractometers are often not used. If water exceeds the target SG, the clock on treatment restarts.

2. Copper treatment - Follow medication recommendations. This can be effective in 2 or preferably 4 weeks of treatment. After treatment, remove all copper and observe fish for 4 more weeks. Copper is a poison to the fish and creates some stress. Be sure not to use copper with live rock or live sand.

3.. Transfer method The fish is moved from tank to tank to separate the fish from the cysts that fall off and the free-swimming stages of the parasite. Two hospital tanks are needed to perform this treatment. The fish should be transferred ideally in a strainer so water is not moved between treatment tanks.

4. Only the above 3 known readily available cures work almost 100% of the time. Other chemicals will kill the MI parasite, but only in special conditions that are not good for the fish Some chemicals will only kill some of the organisms, letting the others escape death to go on to multiply and infect.
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Total Comments 2


  1. New Comment
    Korrine's Avatar
    What are your preferred treatment methods on QT'd fish?
    Posted 12/26/2010 at 12:53 PM by Korrine Korrine is offline
  2. New Comment
    snorvich's Avatar
    I treat only when I see a problem for several reasons: first there are different treatments for different problems, second treating any fish is hard on the fish and I prefer not to do so unless desirable. However I always use prazi.
    Posted 02/12/2011 at 06:43 AM by snorvich snorvich is offline

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