If you raise fish, the most important thing is to keep your aquarium fish happy and healthy. There are a lot of factors that can affect a fish's health. As a fish owner, we should be responsible for maintaining the health of our fishes in excellent condition.
Fish disease is the greatest threat to aquarium fishes.
There are many lower life forms such as virus, bacteria, fungus, protozoan and other parasites that can cause disease to fishes and these are called pathogens. Each aquarium contains pathogenic bacteria and fungus spores as part of its normal flora and fauna. Every fish also carries its own parasites and bacteria, some even come with internal fungus. With all these factors in mind, it may seem surprising that fish are not constantly suffering from disease. Fish, like humans, have their own immune system to fight against diseases.