What is Ich?

Ich is a protozoan disease that is often called 'white spot disease.' The scientific name for the disease is ichthyophthiriasis and the causative agent is Ichthyophthirius multifiliis. It is wide spread in all freshwater fish but appears to be more common in aquarium fish, possibly due to the closer contact and stress involved with aquarium species.

Identifying Ich

The symptoms of ich are very evident and usually include characteristic white spots on the body and gills. In some infections, the ich organisms will only be found on the gills. As the disease progresses, the fish will become more irritated and may try to rub or scratch against the sides and bottom of the tank. The disease may then cause respiratory distress, severe agitation, loss of appetite, and eventually death.

Why Fish Get Ich

Ich is so widespread that many experts feel that it is present in the environment of most aquariums, especially in larger holding tanks, rearing ponds of breeders, collectors, and wholesalers. In fact, just about every aquarium fish will come into contact with this protozoan at several times in its life. Because it is so widespread, most fish have developed a good immune response against the disease to allow them to fight off the protozoan infection before it ever causes any symptoms. Captive fish that develop ich usually get the disease when their immune systems are not functioning as well as they should be because of stress. We know that stress lowers the immune response and when fish are stressed that is when ich is most prevalent.

There are many causes of stress in a fish's life, many of which can be made worse or better by the owner. Water temperature, water quality, tank inhabitants, improper diet, and a variety of other factors all contribute to stress, but one of the most severe causes of stress occurs during shipping and handling of a new fish. Whether coming from the wild or farm-raised, the handling and shipping of the fish from their origin to a wholesaler, then to a retailer, and finally to your home is extremely stressful. With the widespread prevalence of ich, it is no wonder that many newly purchased fish are affected.

Treatment

Since we understand that we cannot kill ich while it is on the fish, we know that moving a fish to a quarantine tank to treat will not solve the problem in the main tank. The time to use a quarantine tank is before a new fish is introduced into a display tank. If a fish in a tank has ich, you must assume that the entire tank is now contaminated with ich and must be treated.

Another way to get ich out of a tank is to remove all of the fish. Since we know that the tomites can only survive for 48 hours without attaching to a fish, if we remove all of the fish and then raise the temperature to 80°, the existing ich in the tank should be dead after 2 days. To be safe, wait 4 days before returning the fish to the tank. But remember, you will need to treat the tank that the fish are moved to, otherwise, fish entering that tank could become infected.

Remember, we are treating the tank, not the fish, so all effective treatments are designed to kill the trophite form of the disease while it is in the tank. The mature ich organisms that cause the problems on the fish do not die from treatment, but fall off in a couple of days during their normal life cycle and then their offspring die from the treatment in the water.

Some of the best treatments historically have been formalin or malachite green, or a combination of the two. Copper, methylene blue, and baths of potassium permanganate, quinine hydrochloride, and sodium chloride have also been used but do not appear to offer an advantage over the more readily available formalin and malachite green products.

When using formalin, make sure to use recently purchased formalin. Formalin that is stored for long periods of time can convert to paraformaldehyde, which can be toxic to fish. An indicator that this has occurred is the formation of a white precipitate in the bottle. Malachite green may also stain some decorations and silicone to a green color and may be toxic to piranhas, neons, sunfish, and some scaleless fish, if given at the recommended dose. For these fish or other sensitive species, they should be treated at half strength and monitored carefully for signs of distress.

While we rarely recommend treating an entire tank for a disease, ich is an exception. Make sure to follow individual label directions, and remove the carbon from your filter and shut off any UV sterilizers or protein skimmers during treatment because they will inactivate or remove any medications that are added.