It is important to know that fishes, just as humans, can get sick and suffer of different diseases. Some of them are easier to treat than others; what is vital to know is how to identify the first symptoms of each disease in order to stop it before the spread cannot be held or reversed.
Some of those diseases are the consequence of the lack of an appropriate hygiene in the tank, infection of wounds caused by another fish, introduction of the fish before it acclimatization of its new environment, or just by stress.
A fish is a creature extremely fragile, which can suffer the consequences of an inappropriate care very easy, which is why it is extremely important to be informed about the different treats that our fish is exposed to. By acquiring this knowledge the owner will be able to act in the most effective way once the symptoms are identified and save the life of the fish which is infected and the lives of the other fishes of the tank before a possible spread.