Common Saltwater Aquarium Fish Diseases

Common saltwater aquarium fish diseases fall into four main categories: parasitic, bacterial, viral and fungal. In most cases, fish diseases show up first with reduced appetite and hiding. When you observe these symptoms, begin to watch for additional symptoms. Begin rapid treatment.

  1. White Spot Disease

    • White spot (Cryptocaryon irritans), sometimes called saltwater ich, appears as small white spots that cover the fish's fins and body. Fish with white spot also flick and scratch. White spot is highly infectious, and requires quick treatment. Caused by a parasite, white spot disease requires a freshwater bath and formalin treatment. Copper-based medicines may help, but are typically not as effective as formalin. An ultraviolet sterilizer might help.

    Marine Velvet

    • Marine velvet (Amyloodinium ocellatum), also called Oodinium or saltwater ich, looks similar to white spot. In this disease, white spots pepper the fish̵7;s body, giving appearance of a thin dusting of white velvet. Marine velvet causes flicking and itching, as well as rapid respiration. Eliminating marine velvet, which is infectious, requires treating both the fish and the tank. A freshwater bath can help get rid of the parasite spores on the fish, and copper-based medications, and ultraviolet sterilization can help get rid of the parasite in the tank.

    Lateral Line Disease

    • Lateral line disease, also called head and lateral line erosion disease, exhibits distinctive symptoms, including obvious erosion of the lateral line, pits in the fish̵7;s skin and faded coloration. The lateral line is a sensory system that runs down both sides of the fish from its head near the eye all the way to the tail. The disease is not infectious--it results from poor water conditions. Several fish might exhibit symptoms. Treatment requires investigating the cause of the poor water conditions and correcting those problems.

    Cauliflower Disease

    • Cauliflower disease (Lymphocystis spp.) produces small cauliflower-like clumps on the fins and body of the fish. The symptoms look severe, but generally do not cause stress in the fish. Cauliflower disease, which comes from a virus, does not have medicinal treatment. A freshwater dip may help, but maintaining high water quality while the fish recovers is generally sufficient.

    Fish Flukes

    • Fish flukes (Benedenia melleni) cause rapid breathing, flicking, cloudy eyes and white patches on the skin. Sometimes, you can see the worm-like attachments of the parasite. This is an infectious disease that can spread rapidly among fish. It also weakens the fish, creating an opportunity for secondary bacterial infections Treatment includes a freshwater dip and proprietary anti-fluke medications.

    Bacterial Diseases

    • A variety of bacterial diseases can infect aquarium fish. They have common symptoms, such as open sores on the sides, rapid respiration, frayed fins and a gray film over the eyes. Bacterial infections typically infect only one or two fish at a time. Treatment includes isolation, reduced lighting and antibiotics.