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 disease or infection 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 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, not quarantining, 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.
