:  Disease
Marine fish diseases are often difficult to diagnose. The parasites that cause disease are usually far too small to see with the naked eye. Most marine fish caught on reefs have some type of parasite in or on their body. They bring the parasites with them into the fish store, and then on to a home aquarium. Thankfully, many of these parasites cannot reproduce in the aquarium and do not cause lethal disease. The few that do are listed below

Marine fish ailments can be caused by such agents as viruses, bacteria, protists, fungi, worms, crustaceans, and environmental factors. The following is a brief list of some of the causative agents of marine fish maladies:

Disease Parasites
  1. Protozoan:
    1. Flagellates (diplomonads):
    2. Ciliates:
    3. Dinoflagellates:
    4. Sporozoans:
  2. Bacteria:
  3. Fungi:
    • Saprolegnia is associated with external fungal infections (controversial relationship - Saprolegnia is a freshwater parasite)
    • Ichthyophonus hoferi is associated with internal fungal infections
  4. Virus:
    • Iridoviruses are associated with Lymphocystis or Nodule Disease

Animal Parasites
  1. Worms
  2. Crustaceans: Isopods and Copepods
    • Isopods: External skin parasites, resembling roly-polies, on fish
    • Copepods: Embedded skin parasites beneath the skin of a fish

Environmental Causes of Disease:
  1. Gas Bubble Disease is associated with fish that have been:
    • Collected at depths over 30 feet and rapidly brought to the surface
    • Exposed to water that is supersaturated with gas
  2. Head and Lateral Line Erosion is associated with a variety of factors, including malnutrition, poor water quality, pathogens, stray voltage, activated carbon, copper, and other things.
  3. Malnutrition is associated with a diet lacking in protein and vitamins
  4. Swim Bladder Disorders are associated with fish brought to the surface too rapidly from deep reefs
  5. Iatrogenic Problems are associated with side effects from medications, such as ammonia build up in a hospital tank due to the death of nitrogen fixing bacteria.