Marine ICH

(Cryptocaryon irritans)

Common Indicators: White spots on gills and body; sluggishness, respiratory distress, irritation.

While it shares a name with the freshwater variety, Marine Ich is a distinct parasite. It’s one of the most common diseases that afflict marine fish in aquariums. This disorder is also commonly mistaken for saltwater velvet disease (oodinium). An early sign of infection is that fish may exhibit behaviors in which they attempt to ‘scrape’ themselves on rocks and other surfaces. In fact, observing your aquarium for these behaviors may allow you to catch infection before the outward symptoms are visible. Fish with Ich can show white lesions or spots on the gills and body. In addition, infected fish may exhibit respiratory distress that can appear as ‘gasping’, act sluggish or hang on either the surface or bottom of your aquarium, and exhibit physical changes such as cloudy eyes or ragged fins. If not treated, Ich is frequently fatal to fish.

The parasite that causes Ich, Cryptocaryon, has three key life stages. During the tomont stage, the parasite lies in the substrate, rocks or other objects and  is encysted; within this cyst, the parasite divides into numerous daughter organisms called tomites.These are free-swimming and aggressively seek a host, as they can live only for a limited time outside a host fish. Once attached to the fish’s gills and skin, they become trophonts. This is the stage that the visible symptoms we associate with Ich present themselves. This feeding stage lasts about seven (7) days. Temperature can affect the life cycle, with higher temperatures speeding this cycle and lower temperatures slowing this life cycle.

New Life Spectrum® IckSHIELD pellets can attack the parasite while in the trophont stage while infesting the fish. IckSHIELD powder water treatment bath solution can kill both the trophont and free-swimming tomite stages. Other treatments, like Copper Sulfate, can only kill the free-swimming tomite stage, while also being more  toxic to fish.

Treatment is recommended for 21 days. This is to break the Cryptocaryons irritans life cycle. When encysted, the organism is resistant to treatment. However, once the life cycle is initiated, it must go through the three stages, with the time for each life-stage pre-determined: the tomite stage of the parasite is a short, and the approximate 7 day feeding trophont stage lasts around  7 days, with the organism having no choice about the length of this stage. By treating for three-times this approximate 7 day lifecycle, the medication is able to catch these parasites as various individual organisms move into the “window of vulnerability” in their three-stage lifecycles.

There are unknowns when dealing with Cryptocaryon irritans: such as whether they can go ‘dormant’ in their encysted stage when conditions are unfavorable (and as such stop infecting the aquarium, but be potential available for a re-infestation during a future time of stress). However, IckSHIELD is safe to use in further treatments; while a 13-day ‘rest’ between treatment cycles is recommended if possible, if re-infestation occurs, it is possible to treat before this period.  See our IckSHIELD Medication FAQ or Documentation for more details.

Prior to setting-up a tank, or reusing a tank for new fish, we recommend filling it with clean fresh water and dosing the water with potassium permanganate to the point where the color has a visible red tint. We let it sit in the solution for a day. We then dry the tank. After this point, we use it for fish. Cryptocaryon irritans is an extremely hardy parasite (particularly in it’s encysted stage) and it is worth the effort to sterilize a tank as a preventative.


Bibliography & Further Reading

Noga, Edward J. “Fish Disease Diagnosis and Treatment.” 2nd Ed. John Wiley & Sons; 2010

Fenner, Robert. “The Conscientious Marine Aquarist.”Microcosm Ltd.; 1998

Stoskopf, Michael K. “Fish Medicine”. W.B. Saunders Co.; 1993

Untergasser, Dieter Ed., “Handbook of Fish Diseases”. TFH Publications; 1989

Moe, Martin A. Jr. “The Marine Aquarium Reference: Systems and Invertebrates.” Green Turtle Publications; 1989

Duijin, C. Van,. “Diseases of Fish.” Iliffe Books UK; 1973


Siegel, Terry, “Cryptocaryon: An Old Enemy” Marine Fish & Reef 2002 Annual; 2002

Advisory: The information contained in this article entry is for informational purposes only, and is not a substitute for consultation with a veterinary professional nor treatment under the supervision of a veterinary professional. New Life International does not guarantee the accuracy or completeness of the information nor of the sources cited as reference. This articles is not a diagnostic tool or reference, nor should be considered treatment advice by New Life International.

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