Fish Disease
Fish are susceptible to numerous diseases, some of which are highly contagious, and prompt treatment is needed to prevent losses. It must be remembered that imported fish can be swimming in your tank within a few days of being caught in an Asian swamp or an Amazon pool, due to speedy air-freighting, and you may unwittingly introduce diseases develop-in in an apparently healthy fish. Conscientious dealers quarantine their fish, but there are some dubious sources from which diseased fish are common. Luckily, most of the common diseases are easy to treat.
Most of the proprietary medicines available are broad-spectrum, killing most disease organ-isms. It therefore does not usually matter if you are unable to identify the precise disease affecting your fish, as the treatment will usually help.
White Spot or ichthyophthiriasis is the most widespread and dangerous disease affecting freshwater fish. It is caused by a microscopic protozoan, Ichthyophthirius, and is highly con-tedious. Small white specks up to lemma (1/32in) in diameter appear on the body of the fish, usually first on the fins. They disappear in a day or so as the parasites drop off and proliferate on the tank bottom, then reappear in progressively greater numbers, cover-in the fish and weakening them so that they die within a few days. The damage to the fish’s protective skin also allows the entry of other types of disease organisms. This disease is always introduced from new fish which have not yet developed signs of white spot. Quarantine prevents white spot spreading in your main tank.
White spot is treated by various proprietary medicines which are added to the water. Some are toxic to plants, and this means that the fish must be transferred to your quarantine/hospital.
Tank for treatment. Detailed instructions will be provided for safe use. Always raise the tank temperature anew degrees during treatment (even if the fish have been transferred to another tank): this speeds up the development of the parasites, which in their free-swimming form will be susceptible to the drugs, or will simply die if the fish have been removed from the tank. With this, as with other diseases, sterilize the net used for handling fish by dipping it in boiling water to kill off the parasites.
Dominium, or velvet, is another common disease, and usually follows chilling; a related disease affects marine fish. Dominium resembles white spot, but the spots are very small, and affected fish look as though they have been dusted with white powder. The microscopic parasites are present inmost tanks, but do not cause obvious disease unless the fish are weakened by chilling or other problems. Even then. Only a few fish are usually affected, the most susceptible types being Cyprinids. Labyrinth fish and Egg-laying tooth-carps. Once again, proprietary drugs are available for treatment, which isn’t usually difficult.
Tuberculosis is common among imported fish, or fish which have received a poor diet. Affected fish are lethargic and become hollow-bellied. With inflamed gills. It is not particularly
Infectious, and never affects humans. Infected fish are best disposed of humanely.
Dropsy is not a disease, but a symptom of other illnesses. The fish be-come bloated with fluid, so that the scales stand out like a pine cone. It is incurable, and affected fish should be humanely killed.
Flukes are parasitic flatworms, sometimes affecting imported fish. They have an extremely complex life-cycle, involving birds, crustacean or snails as alternate hosts so cannot normally spread in the aquarium. They some-times cause an infected fish’s eyes to bulge, and lead to blindness. The con-diction is untreatable.
Fungal Infections are quite com-moon after some damage to the skin or fins. They appear as a cotton-wool-like growth, usually on the fins, and grade-ally spread over the body. Fungus is easy to treat, by removing the infected fish to the hospital tank and immersing it in water to which sea-salt has been added at a rate of half a teaspoonful tone liter of fresh water (’/4teasp/pint).Alternatively, various proprietary treatments are available. Brackish- water fish kept in freshwater are particularly susceptible to fungus (notably Tetraodon fluviatilis and Scatophagusargus), and for this reason seldom thrive in the freshwater tank.
Crustacean Parasites are uncommon in the aquarium, but are some-times introduced with live
Daphnia. The Fish louse, Argyles, is a 5mm (3/16in) shrimp-like organism which clings to the fish and feeds on blood. These parasites are easily seen; if the fish is caught in a net, the Fish lice cane rubbed off or picked off with tweezers. Anchor worms look like worms, but are actually crustaceans. They are up to 2cm (3/4in) long, and threadlike, burrowing into the skin of the fish and feeding on its tissue. Anchor worms can easily be seen, and are killed by catching the fish and painting the worms with 1 per cent potassium per-
Manganese solution (don’t let this get into the gills of the fish). Do not try to pull the worms off, as they are firmly anchored in the skin.
A seriously ill fish is a menace to its tank-mates, and should be disposed of. Do not flush fish down the toilet; this is in-humane. A fish can be killed instantly by throwing it hard against a solid floor.
Fish diseases are not transferable to humans. There have, however, been rare reports of a skin condition caused by organisms living in very unhygienic and badly kept aquaria, which enter the skin through cuts and abrasions. So, if you have an open wound on your hands, it makes sense to wear household rubber gloves when working on your tank.