Signs of a Sick Fish

Fish can be afflicted with hundreds of different diseases, many of which can be difficult to recognize and treat. Unlike other pets, fish cannot communicate when something is wrong, so their diseases often go unnoticed. However, a number of tell-tale signs will help you recognize diseases in your fish. Most of these signs fall into one of three categories---tank appearance, fish appearance and fish behavior.

  1. Tank Appearance

    • The first signs of sickness amongst fish may show up in the tank. Indicators include cloudy water, foam floating on the surface of the water, uneaten food, and dead plants or fish inside the tank. Many times, these signs indicate problems with your tank's filtration system that may be making the rest of your fish sick. Dead fish may be the first signs of an epidemic that has the potential to spread to the rest of your fish.

    Fish Appearance

    • The appearance of your fish is another excellent indicator of their health. Bulging or sunken eyes may indicate gas bubble disease, a tumor, a parasite or a bacterial infection. Cloudy eyes, bloody eyes and eyes that change in color may also indicate health problems. You should also look at your fish's belly to see if is looks sunken or bloated, as this may indicate malnourishment or other problems. Check the skin and scales on your fish for symptoms as well. For example, notice if any of your fish have white spots, dark spots, bloody sores or if their bodies look slimy. Sick fish may also have frayed fins or fins that appear to be clamped to the body. Injuries such as torn fins or missing scales may result from being transported from another tank or having a fight with another fish. Look to see if your fish have any noticeable tumors, growths, ulcers, parasites or other deformities.

    Fish Behavior

    • Fish behavior is another important indicator of health. Examine your fish's breathing to see if it appears to be gasping or breathing unusually slowly. It is also unusual (in most breeds of fish) for the fish to breathe by putting its mouth above the surface of the water. If your fish tries to jump or spit above the surface of the water, this may indicate disease. A fish's swimming pattern can also give significant indications about the fish's health. See if any of your fish are swimming sideways, tilted or constantly dwelling on the surface. Also, notice any apparent lack of control, such as swimming up and then drifting down, swimming with the head up and tail down, or swimming in an uncharacteristic part of the tank. Finally, sick fish may twitch, thrash or scratch their bodies on decorations in the aquarium.