Despite the popular opinion that tropical fish are not affected by Ich because of their warm water temperature, both freshwater and marine fish can contract Fungal Ich. Since there's no treatment known to cure Fungal Ich, you should remove and humanely destroy infected fish and try to prevent the infection from spreading to other fish in your tank. The disease is transmitted when an infected fish dies and is eaten by another fish. It can also be transmitted through infected, live fish food. The internal organs attacked by this fungus are the liver, spleen, heart, kidney and brain.
Death occurs when the organs are no longer able to function.
Parasitic Ich or White Spot is caused by the Ichthyopthirius multifiliis parasite, and is associated with small white spots visible on the outside of freshwater fish. The only way to truly diagnose Fungal Ich or Tumbling Disease is through the autopsy of a dead fish. During the autopsy, white cysts, which are usually visible to the naked eye, will be found on the internal organs. For accurate diagnosis, specimens from the liver, heart, spleen and kidney should be viewed under a microscope at 50x to 100x magnification. Fungal Ich cysts are round brown with black particles inside and enclosed in pale connective tissue.