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Cryptocaryon irritans, marine white spot disease, marine Ich


Symptoms: small white spots, nodules, or patches on their fins, body, or gills. Fish may produce excessive slime, show problems breathing (ich invades the gills), have frayed fins, loss of appetite, and cloudy eyes. White spots may not be obvious on light colored fish or if the infection is just in the gills. Other indications can include rubbing or scratching against decor or substrate, abnormal swimming, hanging at the surface or on the bottom, acting lethargic, or breathing more rapidly as if in distress.

Marine Ich, Crypt, or Marine White Spot Disease is one of the most common maladies experienced in the marine aquarium, with the other being Marine Velvet, and is attributed to a ciliate (a protozoa) bearing the name of cryptocaryon. Cryptocarion is often confused with velvet disease (Oodinium). Since the treatments for these two diseases are completely different, the diagnosis must be certain. The Cryptocaryon spots are much larger and can be seen clearly. The spots in the case of Oodinium are so small that it appears more like the fish has had powdered sugar sprinkled over it. It is hard to discern individual spots. The differentiation is easier under the microscope: Oodinium organisms look like black balls at a 100 – 200 magnification. Ichthyo and Cryptocaryon organisms contain a clear, horseshoe-shaped nucleus on the inside.

This disease can appear in environments with excessive stress, poor water quality and fluctuations in water temperature. It can also come into the aquarium on a new fish that is a carrier.

This protozoa has four phases to its life, lasting up to 38 days depending on the temperature of the environment. This parasite affects marine and brackish fish. Aquarists are most familiar with the stage where the protozoa is infesting the host, with small white spots on the fish's body and fins. Unfortunately this visual clue is also the reason for difficulty in eradicating marine ich. Once the parasite has left the host's body many aquarists believe their fish is cured and the problem is solved and so they cease treatment, only to have another larger reoccurrence.

For eradication treatment must be carried through to completion, so understanding the parasite's life cycle will greatly increase your chances of success. The life cycle is outlined here:

  • Trophont phase - when the parasite is growing in the skin or gills of the fish it appears as small white nodules, and the fish begins showing signs of irritation. It will spend 5 to 7 days (depending on the temperature) feeding on the fish. Once it reaches maturity it leaves the fish, reportedly after the lights go out. It is now called a protomont.
  • Protomont phase - the protomont will free swim or will crawl about the substrate for several hours (2 to 18 hours) producing a sticky wall around itself with which it is able to adhere to a surface. Once it adheres it begins to turn into a cyst and is now called a tomont.
  • Tomont phase - at this stage there is rapid cell divisions occurring, resulting in hundreds of daughter parasites that are called tomites. This stage can last anywhere from 3 to 28 days. Eventually the tomites hatch and begin swimming about looking for a host and are now called theronts.
  • Theront phase - newly hatched, they are swimming about looking for a host which they must find within 24 hours or they will die. Once a host is found they turn into trophonts and the whole cycle begins anew.

The life cycle of this parasite can vary dramatically and is dependent on temperature. Optimal growth of most strains of Cryptocaryon appear to be about 23–30°C, and they cycle faster in a warmer environment. A common mistake is to confuse the treatment of this protozoan with the treatment for freshwater Ich (Ichthyophthirius multifiliis). Raising the temperature of the tank does not help eliminating this protozoa like it does with freshwater Ich.

Ideally the parasite would be eliminated while on the host or shortly after leaving the host. However, those that are buried in the gills are immune to treatment until they leave the fish. This along with the variability of the cycle makes it difficult to treat in such a timely manner.


Please remove any activated carbon from the filter for the duration of the medication use. UV-C appliances and CO₂ fertilizing appliances also need to be switched off. Please also ensure that skimmers and ozonisers in saltwater are switched off. Change 50 % of the water prior to application of any medication. Aerate the aquarium using a diaphragm pump with airstone during the treatment. Filter during the treatment. We recommend cleaning the filter prior to the treatment.

To rid the aquarium of this protozoa, it is recommended that you use a combination of water changes and chemical treatment, a multiple number of times. A common mistake is to confuse the treatment of this protozoan with the treatment for freshwater Ich (Ichthyophthirius multifiliis). Raising the temperature of the tank does not help eliminating this protozoa like it does with freshwater Ich.

Chemical Treatments:

  • Chemical treatments for this disease include using copper, formalin, or a combination of copper and formalin. Follow the instructions provided by the manufacturer. Achilles Tangs are sensitive to copper based products so use them carefully. Equally effective is a short “dip” with Formalin (see directions on bottle for the dip) for these patients, and remove them to a separate tank.

Natural methods include:

  • Low Salinity Method: For low salinity keep the specific gravity of the water at approximately 1.009-1.010 with temperatures of 25 - 27° C for 14 days. A problem with this method are that lower salinities are not as easily tolerated by many common tropical marine species, including angelfish and deep water fish. These types of fish have a much shorter time that they can tolerate the lower salinity. A danger with with using low salinity is in re-acclimating the fish to a higher salinity. You must be able to accurately measure the salinity and must increase it very slowly.
  • Dip Method: Using freshwater or lower salinity dips, either with a duration of just a few minutes, or short to prolonged immersion baths (duration in hours to days) can be used for tolerant fish to kill or reduce the numbers of external parasites on the fish. Unfortunately trophonts and tomonts are more protected, so longer dips and baths are needed than for other parasite species.
  • Water Change Method: For the water change method, replace 50% of the aquarium water daily for 14 days. This is perfectly safe method as long as temperature and salinity are the same, and this will remove the parasites while in a free swimming stage.

Reportably some healthy fish can develop a limited immunity. It may not be a total immunity, rather being just a small amount of infestation rather than extensive infestation. This immunity is short-lived lasting only about six months.

After treatment

After the treatment, please filter the aquarium water for 24 hours using activated carbon to remove the residues of medication. Afterwards the activated carbon should be duly discarded. The addition of a bacterial starter to the aquarium water helps to replace any purifying bacteria which may have been affected. Please check during the treatment and daily in the first days after the treatment the ammonium/ ammonia and nitrite values. With nitrite values of over 0.5 mg/l an immediate water change of 50% should be carried out and a bacterial starter added.

Possible medication:

JBL Punktol Plus 125/ JBL Punktol Plus 250/ JBL Punktol Plus 1500 sera costapur

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