More aquarium fish are killed by disease than any other cause. Unfortunately this affliction could be easily avoided as it's usually cause by poor water quality. Poor water quality can be caused by too many fish in one tank, lack of maintenance of your fish tank aquariums or overfeeding your fish.
In some instances, you may also introduce disease into your aquarium by putting a new fish to an existing tank that has a pre-existing disease from the store. You should always be sure to inspect all fish in a store aquarium for signs of illness before you buy any. Even if the fish you want to buy looks healthy, if there is evidence of other disease in the aquarium, avoid buying from that tank.
Common Aquarium Fish Diseases:
Fin rot is caused by bacteria within the tank and can actually rot your fish's fins away. An injured fish is most susceptible to fin rot as bacteria then has a chance to infect the wound. Stressed fish are more likely to develop bacterial problems as their immune systems are already compromised, however healthy fish are usually able to fend off infection by bacteria.
White spot is easily diagnosed by visible little white spots on your fish. White spot, or Ichtyopthirius, is a tiny parasite that clings to your fish's scales and feeds off the soft tissue beneath. Once you have white spot in your aquarium, the rest of your fish may quickly become afflicted too.
Hole In The Head
This ominous-sounding aquarium disease can actually create little pits in your fish's head. These can look like little dents or dots and is thought to be caused by water that is too high in nitrates. If you notice any pitting or tiny dimples in your fish, then you should immediately test your water levels for nitrate levels. If you find the levels are higher than they should be, then you need to change your water.
Fungal infection is often misdiagnosed in aquarium fish as bacterial infection, so be sure you look carefully at the symptoms your fish is displaying. An injured fish is most susceptible to developing fungal infections. In aquarium fish, a fungus growth at or around an injury should appear a little like fluffy white cotton. If you notice fungus on any of your fish, you should change the water at once and monitor that fish closely.
While most aquarium fish diseases can be controlled by keeping your water clean and changing it regularly, it's still important to be sure you do not buy fish with pre-existing disease from the store. You should also be careful not to put too many fish into one tank. Fish live naturally in carefully balanced ecological conditions so you need to be sure you keep the temperature right for your fish. Maintain your aquarium regularly and your fish should be able to enjoy long happy lives.