Fish diseases

Fish get sick due to stress, wrong parameters, bacteria, parasites or viruses. Recognizing symptoms early makes the difference between an easy treatment and a fatality.

Detailed explanation

Prevention is always better than cure. Most fish diseases are caused by stress: unstable parameters, overpopulation, aggressive companions, inadequate food. A stressed fish has a compromised immune system and becomes vulnerable to pathogens that it would normally keep under control.

Ichthyophthirius (white spot disease, Ichthyophthirius in freshwater aquariums, Cryptocaryon in marine aquariums) is the most common disease. White dots like grains of salt on the body and fins. It is treated by raising the temperature to 30°C (In freshwater aquariums) and with medicines based on malachite green or formalin. Copper (copper sulphate) is used in marine aquariums but NEVER in an aquarium with invertebrates.

Bacterial infections manifest themselves with eroded fins, ulcers, protruding eyes (exophthalmia), swollen belly (dropsy). They are treated with specific antibiotics. In Italy many require a veterinary prescription.

External parasites (Oodinium, Costia, Trichodina) cause a whitish film on the skin, rubbing against surfaces (flashing), accelerated breathing. Treatments vary by type of parasite.

Intestinal worms are more common than you think, especially in imported fish. White, stringy stools and weight loss despite the appetite are the classic symptoms.

Quarantine is the best prevention. Any new fish should pass 2-4 weeks in a quarantine aquarium before entering the main aquarium. In marine aquariums, quarantine with preventive copper treatment is almost mandatory.

Medicines should never be used in marine displays with invertebrates. Copper kills shrimp, crabs, snails and corals. It always comes in separate hospital aquarium.

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