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Whitespot / Ick

Affected fish

All species, some loaches are particularly prone. The effect on fish within an aquarium is often dependant on the fishes prior exposure to the parasite, since a good immune response can be built up. One of the most common aquarium fish diseases.


The parasite Ichthyophthirius which can be introduced into the aquarium whilst attached to other fish, through infected water or even on plants and gravel. The parasite has a number of stages in its life-cycle; The parasite when attached to fish is enclosed in a cyst (the visible spot) which eventually ruptures and the parasite sinks to the bottom of the aquarium, it then re-cysts and multiplies before releasing a free-swimming stage into the water which must re-infect fish within 48 hours. The whole cycle varies in timescale and is quicker in warmer water, usually taking about a week in tropical aquariums. The disease usually occurs as a result of stress caused by a number of factors, most commonly bad water quality, transport stress, and temperature fluctuations are to blame. Since the parasite is common in aquariums, new fish, which are stressed from transport, often become infected. In this situation the new fish have little immune response and infection allows the parasite to multiply, infecting existing stock. Retailers are familiar with this scenario since they often get the blame for the disease when it was in fact already present in the fish keepers aquarium


Easily identified by small (0.5mm) white specks or spots on the body and fins. Depending on the level of infection there may be just a couple, or hundreds, and it often affects one species more than another.


Quarantining of all new fish, and applying a disinfectant treatment to all plants are good methods of preventing immediate outbreaks. It is likely however that at some stage the parasite will be introduced to the aquarium in which case the only prevention is good fish husbandry, allowing fish to develop an effective immune response.


There are a number of whitespot treatments available in aquatic retailers which are effective. Virtually all treatments only affect the free-swimming stage so they are usually applied over a seven day period in order to catch the parasite at that stage, whenever it occurs within the seven days. Because of this it is important to continue the treatment course even if it appears the infection has gone. Many sources also site a change in temperature and the addition of salt as helpful aids to treatment. Some forms of whitespot may lie dormant for periods, or even spread without a typical free-swimming stage. In these cases treatments will not work and the only remedy is to provide ideal conditions, allowing the fishes own immune system to take care of the problem.

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