White Spot Disease: Symptoms, Causes, and Treatments

White spot disease (Ichthyophthirius multifiliis, or Ich) is one of the most common parasitic diseases affecting tropical fish. Unfortunately, it is also a very persistent disease.

White spot is caused when a protozoan attacks and attaches itself to a fish’s body, fins, and gills. The white spots that appear look like grains of salt or sugar, but each one is actually a tiny parasite. They are very damaging to the fish and can cause breathing and mobility problems and even death.

Once the parasites are established in an aquarium, it is difficult to control the infection because they reproduce quickly. If not controlled, there is a 100% mortality rate of the fish in the aquarium. White spot is very contagious. When one fish in a tank gets sick, it won’t be long before the rest of the fish will start showing symptoms.

However, with careful treatment of the aquariums fish, water, ornaments, and plants, the disease can be controlled.

Diagnosing White Spot Disease

In the first phase of the illness, before white spots appear, infected fish will display some or all of the following behavioral changes:

  • scratching against stones and decorative objects (the parasite has crossed the protective mucous membrane that covers their skin)
  • disordered swimming
  • fins folded against the body

When white spots appear, they are about the size of the head of a pin. The first spots will appear on the fins and can be seen in direct light. As the disease progresses, more spots appear on the rest of the fish’s body.

If the gills are affected, the fish may swim to the surface more than usual. This is because they are having difficulty breathing. When the peri-orbital tissues and the eye muscles are affected, the eyeball will protrude.