Signs Of Infection

Fish may rub against hard objects and swim with clamped fins. Small white spots (1-2mm), initially seen on the fins but eventually visible all over the body including the gills, are characteristic of this parasite.

Fish Affected

All aquarium fish are suspectable.

Details Of Infection

Caused by the parasite Ichthyophthirius multifiliis. The parasite has a simple life cycle lasting just over 3 weeks. Highly mobile free swimming larvae must find a host fish within 48 hours of hatching before they die. Once on a host, they penetrate the skin and feed on the underlying tissue and body fluids. It is at this stage they appear as white spots on the fish. They can remain on the host and grow for up to 20 days. Growth ceases at temperatures below 50°F and is fatal to the parasite above 84°F. However, growth is most rapid at tropical temperatures and the cyst is highly infectious.

Once mature, the Ichthyophthirius multifiliis parasites fall from the fish and attach themselves to any solid object. Here, they encase themselves in a protective membrane and begin to multiply by division. After around 18 hours, the membrane opens releasing up to 1000 new larvae and so the cycle begins again.

Fish are especially prone to white spot if transported for some time and exposed to a prolonged temperature drop. Similarly, aquariums placed near windows or doors may be subject to drafts that can initiate the parasite.

Treatment

Sometimes rasing the temperature can stall the disease but may prove too stressful for some fish. The best cure is to attack the parasite in the free swimming stage with a commercial chemical remedy containing Malachite green. These treatments are very effective and these should be applied on days 1,2,3 and 6 to attack all existing and new free swimming larvae during their 48 hour search for a host. Treatment should continue for up to 2 weeks after all visible signs of the parasite have gone as the parasite may still be present in the substrate in their "gestation" stage or may just be emerging from the fish. Read the instructions on chemical treatments carefully as some treatments are not suitable for small scaled or scaleless fish such as elephant fish or loaches.

Survivors of White Spot usually acquire an immunity to reinfection however they may remain carriers without showing signs of infection.