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Self-Improvement & Hobbies


Learn about parasites, and how to know when they’re troubling your fish
CATS Classified In The Straits Times - September 18, 2010
By: Wong Wei Chen
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Parasites in fish are natural, and quite common. Small numbers do not usually pose a problem, but the catch is that these little buggers are tremendously prolific. When parasites reproduce unchecked, they pose a very real threat to fish and they can quickly do so to your entire aquarium.

Types of parasites
Parasites can generally be classified as ectoparasites or endoparasites. The former are found on the external surfaces of fish such as skin, fins and gills, while the latter are found in internal tissues and organs.

Different types of parasites cause different behaviours and lead to different symptoms, so it’s important to be able to recognise them early.

Follow these steps to see if a fish has been infected:

    A fish infected by ectoparasites usually suffers a body itch. As a consequence, you’ll see it rubbing against various objects in the aquarium. Such behaviour may result in the loss of scales or tearing of skin, which may, in turn, give rise to secondary infections caused by bacteria and fungus.
    Parasites are attracted to the soft tissues within a fish’s gills. When infected, the gills get damaged over time. The fish will then experience breathing difficulties, and will be seen gasping for air at the water surface.
    Check for worms, leeches or flukes on the fish’s body. If possible, manually remove visible parasites from the fish. Follow-up treatment is vital to prevent secondary infections.
    See if your fish has cloudy eyes, or white patches on the body. These symptoms could be caused by fish lice.
    If white spots appear on a fish’s body, making it look like it has been sprinkled with salt, it is likely to have been infected with ich. It may also display symptoms such as loss of appetite, withdrawal and clamped fins.
    Keep a lookout for white or gold speckles resembling powder on the fish. It might have been infected with velvet, a common disease resembling ich. Like ich, velvet may cause the fish to clamp its fins tightly against its body, and seem unstable when swimming.
    Unlike external parasites, endoparasites are relatively rare among aquarium fish. Since they cannot be seen from the outside, you’ll have to observe the fish’s behaviour. Listlessness, loss of appetite and erratic swimming behaviour could be symptomatic of internal parasitic infection.

Treatment of parasitic diseases can be difficult, as most amateur aquarists are ill-equipped to do a proper diagnosis. If the infected fish is an arowana that cost you a bomb, or a pet goldfish that you absolutely love, try a veterinarian.

Most hobbyists, however, will opt for either a salt treatment or disease-specific medication off the shelves, then hope for the best. Where parasitic infections are concerned, prevention is way better than cure!

Fish have a layer of mucus (or cuticle) on their bodies which gives them some protection against parasites. In healthy fish, this layer is continually sloughed off, making it difficult for smaller parasites to anchor themselves permanently onto the fish’s body. In addition, the cuticle contains various substances – such as lysozyme and antibodies – that are believed to have anti-pathogenic properties.

When fish are stressed or when water conditions are poor, the protective properties of the cuticle can be severely compromised, giving parasites the opportunity to proliferate. Keeping tank conditions optimal should therefore be your first line of defence against parasitic diseases.


Fungal infection