Just like humans, fish are plagued by a rich assortment of different diseases. Malicious viruses, bacteria, and parasites are common in aquariums and even normally harmless or even beneficial organisms can become a serious threat when the fish is weakened by stress, unsuitable water chemistry or temperature, inappropriate food, fights with other fishes or similar problems.
Some of the most commonly found diseases in aquariums are the White Spot Disease / Ich / Ick (Ichthyophthirius multifilis), Velvet (Oodinium), Dropsy, Fin Rot, Anchor Worms, Gill/skin flukes, Head Hole disease (Hexamita), Tuberculosis, Marine Velvet (Amylodinium), and Marine-white Spot Ich/Ick (Cryptocaryon).
The best way of dealing with the fish disease is to prevent an outbreak in the first place. Curing an infestation is much more difficult and all remedies have side effects.
- Keep your fish healthy and stress-free to boost their immune system.
- Prevent the introduction of new and potentially dangerous microorganisms to the aquarium.
The first point involves providing your fish with a suitable environment. Never mix fish species that require very different parameters to do well. Read more about each species and provide it with the right water temperature, pH-value, water hardiness, aquarium set up, space, water quality (i.e. levels of soluble waste), oxygen, salinity, etcetera. Choosing suitable aquarium companions is also important. Bullying and/or fighting is very stressful and can also cause wounds. Some species are schooling and must be kept in larger groups, some prefer to live in pairs or harems, and others should never be forced to live together with members of its own species unless you intend to breed fish. The diet should be similar to what the fish would eat in the wild. Choosing high-quality food and giving the fish a varied diet promotes a strong immune system.
The second point involves never placing anything in the aquarium without first minimizing the risk of introducing potentially dangerous organisms. Living things, such as fish, invertebrates and plants always carry free-passengers and guaranteeing new purchases is, therefore, a good idea. Dead things, such as gravel, equipment, and artificial plants can also carry stowaways, but with dead items, a good cleaning can be performed that kills of all living creatures. A problem arises when you do not wish to kill off organisms, e.g. when you use gravel from an old aquarium to introduce beneficial bacteria to a newly set up aquarium.