The Symptoms of Aquarium Fish Diseases

There are a number of common diseases found in aquarium fish, many of which are easily spread through the water column to other tank inhabitants. Because many of these illnesses can progress rapidly if left untreated, identifying early symptoms of common disease and illness in your aquarium fish may be the key to saving the lives of your fish and preventing further illness in the future.

  1. Lethargy

    • Decreased energy or prolonged periods of inactivity are often amongst the first signs of illness in fish and can be a symptom of parasites, toxic shock, or infection. Immediately investigate any abnormal or abrupt change in activity level, as it is frequently found in conjunction with other symptoms that may point to more specific diagnoses.

    Flashing or Scratching

    • Fish that "flash" (dart abruptly across the tank) or attempt to rub against tank decorations or the glass are almost always affected with some sort of external parasite. Flukes and ich are perhaps two of the most common external parasites: flukes are small flatworms which can sometimes be seen hanging off of the gills and skin, while ich (also called white spot disease) is characterized by small white speckles across the fish's body. Velvet is another common parasite which causes these behaviors, but it is often smaller and more metallic in appearance than ich.

    Lack of Interest In Food

    • When fish suddenly go off of their food, it can often be an indicator that something is amiss either with water chemistry or the fish itself. Swim bladder disease and Hole in the Head Disease are two illnesses associated with diminished appetite, and both can be fatal if not treated early on. HITH disease is particularly fast-acting, especially in warmer water, and is almost always accompanied by other symptoms, such as facial scale damage, even in early stages.

    Fin or Scale Damage

    • Several types of fungal infections can cause scale loss, most frequently around the head and gills, or tear-like deterioration of the fins. Dropsy, a potentially fatal illness common in labyrinth fish such as goldfish and bettas, is also characterized early on by raised, pinecone-looking scales.

    Color Changes

    • While stress is the predominate factor in lackluster color, ammonia toxicity and internal parasites or infection can also cause fading. The appearance of stress stripes or other patterning that is not usual to the fish or species should always be treated as a potential illness, and other symptoms should be evaluated before medication is administered.