Marine Ich (
Cryptocaryon irritans)
Symptoms: Salt-like specks on the body/fins. Rubbing or scratching against decor or substrate, Excessive slime. Problems breathing (ich invades the gills), Frayed fins, Loss of appetite, Cloudy eyes, Abnormal swimming.
Marine ich or white spot disease is one of the most common maladies experienced in the marine aquarium, with the other being Marine Velvet. 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, the small white spots similar to a sprinkling of salt 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, they cycle faster in a warmer environment. 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 a timely manner.
So 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.
- Chemical: Chemical treatments for this disease include using copper, formalin, or a combination of copper and formalin. Follow the instructions provided by the manufacturer.
- Natural: Natural methods include either a quarantine tank with a low salinity (hyposalinity) or large frequent water changes. For low salinity keep the specific gravity of the water at approximately 1.009-1.010 with temperatures of 78 - 80{deg} F (25 - 27{deg} C) for 14 days.
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. 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. This immunity is short-lived lasting only about six months and may not be a total immunity, being a small amount of infestation rather than extensive infestation.