The ability to quickly identify and treat common fish diseases greatly improves the odds that sick fish will bounce back to good health. Key to disease control is observing fish behavior. Any lasting changes to normal behavior should be investigated. When fish start acting differently, it’s time to take action. Even just a day or two of an undiagnosed disease can be disastrous.
Fish disease can be parasitic, bacterial, viral or fungal. Common signs of fish disease include loss of appetite, lethargic or abnormal swim behavior, and an obvious wound. Another symptom is “flashing.” When fish are flashing, they roll over on their sides as if trying to scrape something off their bodies.
If these symptoms occur, consider hiring a professional to help. A professional’s know-how is often critical to treating sick fish without hurting the rest of your pond population.
A common fish disease is ichthyophihirius multifilis (known as ich).This parasite free floats until it finds a host. Symptoms your fish have ich include flashing off the bottom, erratic spurts of activity, thrashing about, and jumping out of the water. The parasite generally attacks the gills, skin or fin tissue of the fish. Ich can be seen by the naked eye, appearing as gray-white specks on the skin.
The best defense against any parasite attack is prevention. Having a clean water source free of pathogens and maintaining good water quality help protect your fish. It’s also important to quarantine new fish for one to two weeks to determine if ich is present and to maintain a 2 to 3 percent salinity level.
When treating for ich, conduct daily water changes for one to two weeks, maintain a salinity level that is safe for your particular fish, provide supplemental aeration, and clean out areas that collect waste such as gravel beds, spaces between rocks, filter pads and plant containers. You may not be able to save the infected fish once the spots appear, but you can help protect the rest of your fish population. If the treatment does not work you may need to buy “anti-ich” medications or contact a fish health specialist.
Columnaris is a bacterial disease that commonly causes external infections. Columnaris shows up as grayish lesions on the body, gills or fins that rapidly increase in size and become irregular in shape. The lesion may have a yellowish color due to large aggregations of the bacteria.
Proper diagnosis of the disease is best accomplished by microscopic examination. Sometimes the wound can be healed by applying iodine with a cotton swab.
Columnaris is commonly associated with stress to the fish. Handling fish, overcrowded conditions, poor water quality, high water temperatures, low dissolved oxygen, and external injury all stress fish. Minimizing stress on your fish will help to prevent bacterial diseases.
Viruses are the most infectious diseases of fish because they are untreatable and there are few approved vaccines for their prevention. One of the best known viral diseases is viral hemorrhagic septicemia (or VHS). Formerly thought to be confined to Europe, VHS has been found in marine fish as well as freshwater fish in North America. In 2006 the disease was determined to be the cause of high fish mortality in the waters of Lake St. Clair, Lake Erie, Lake Ontario and the St. Lawrence River.
VHS outbreaks affect fish of all ages and occur during all seasons but are most common in spring when water temperatures are rising or fluctuating and fish immune systems are suppressed. The best defense against the disease is prevention. Whether native or an ornamental species, know where your fish are coming from. Many fish species are required to have health inspections performed to certify that the fish are free of VHS and other fish diseases. Contact your local conservation office for more information on regulated fish species in your area.
Fungal diseases are typically a second invader of tissues damaged by trauma, infectious disease or poor environmental conditions. The most common fungal diseases affecting fish are the Saprolegnia species. Their presence is often noted by a white to off-white, cottony growth that can ultimately cover the entire fish.
Control of the fungus, as with other fish diseases, is best achieved by maintaining good water quality and minimizing stress on the fish.
Treating sick fish is best done using chemical-free methods. If chemicals are needed to treat sick fish, consult a professional with the capabilities to accurately diagnose and treat disease.
Prevention, however, remains the key to optimal fish health. As the old saying goes, “the best offense is a good defense.”