How to Identify & Prevent Saltwater Ich (Cryptocaryon irritans)

Saltwater Ich (also known as Saltwater Ick and White Spot Disease) is one of the most common diseases that infect marine fish in home aquariums. It is caused by Cryptocaryon irritans and is similar to Freshwater Ich. Infection with Cryptocaryon irritans is often confused with another common saltwater disease Velvet caused by the Amyloodinium parasite. Therefore, proper identification is necessary for correct treatment and prevention of this disease.

Cryptocaryon is a fully ciliated protozoan that is present in all saltwater environments. It is prevalent in marine aquariums, aquaculture ponds, and in import and wholesale holding environments. This widespread protozoan penetrates the skin and gills of the fish. Depending on the immune status of the fish, it can cause symptoms as mild as just a few small white spots to more severe symptoms including severe irritation, loss of appetite, lethargy, severe respiratory distress, and death.

Most wild fish are exposed to low levels of this parasite but are able to effectively fight off the infection without becoming seriously ill. In contrast, due to a relatively small volume of water and a concentrated population of fish in the home aquarium, the number of Cryptocaryon has the opportunity to explode. Elevated levels of stress caused by poor water conditions, improper diet, or aggression from existing tank mates can further aggravate the situation. As a result, even low, non-problematic numbers of Cryptocaryon protozoan can rapidly cause serious infections.

Cryptocaryon irritans is not too difficult to identify because of the characteristic white spots that appear on fish. The white spots are 0.5-2.0 mm in size and typically appear first on the pectoral fins. As a result, infected fish may swim with folded or clamped fins. As the disease progresses, the spots will become more widespread, and the eyes of the infected fish may become cloudy. A secondary fungal infection may also appear on the skin. If the infection is concentrated in the gills or is in the early stages, the fish may show irritation, respiratory distress, and lethargy without having any visual spots.

The treatment for Cryptocaryon irritans is fairly straightforward provided the cause of the stress is corrected. By far, the most popular and effective treatment is copper. There are a variety of copper products available for use in the home aquarium. These copper-based medications will provide proper treatment, if used at the correct dose.

A word of caution: even at extremely low amounts, copper is very toxic to invertebrates and can never be used in reef aquariums or aquariums with invertebrates.

To ensure proper treatment, move the infected fish to a bare bottomed quarantine or treatment tank. It is essential to follow the manufacturer's instructions and use a copper test kit to monitor and maintain therapeutic levels of copper. Other methods that are sometimes used to control both freshwater and marine ich are high wattage UV sterilizers and diatom filters. The exceptionally fine diatom filters can help strain Cryptocaryon out of the water during its free-floating stage. A properly sized UV sterilizer will also kill the free-floating Cryptocaryon.

The old saying that "prevention is the best form of medicine" is absolutely true of all marine disease . It is especially true of Cryptocaryon irritans. Some of the steps that can be taken to aid in the prevention of disease include:

1. Place all new fish in a quarantine tank for at least 2-3 weeks to make sure they are eating, free of disease, and are able to recuperate in a stress-free environment. Keep in mind that the quarantine tank must be clean, appropriately sized with efficient filtration, and have proper water parameters.
2. Properly treat any sick fish before introducing them to the main display aquarium.
3. Provide adequate hiding places to further decrease fish stress

Remember, stress is the enemy of fish health. Cryptocaryon will target stressed fish with lowered immune systems. Reduce fish stress to decrease disease incidence.

Good husbandry practices such as maintaining water quality, correct nutrition, stable temperature, and meeting habitat requirements contribute to the overall health of your aquarium inhabitants.