About Freshwater Tropical Fish Diseases

A diseased fish must be treated quickly in order to keep it from dying or infecting other fish in the tank. Fish diseases are caused by bacteria, low water quality, overfeeding and neglect. Most freshwater tropical fish diseases are treatable and prevented by keeping the tank free of bacteria, changing the water consistently, maintaining the filtration system and properly feeding the fish.

Common Diseases

• Dropsy: Dropsy is an internal bacterial infection, where the scales on the sick fish are raised and the fish looks bloated. If caught early, medications may prove effective. However, by the time the diagnosis has been made in most cases, the chances of survival are small. Changing the water daily and improving its quality may be helpful. Dropsy is not contagious to other fish.


• Ichthyophtirius, or White Spot Disease: A fish appears as if white salt granules are on the body, especially around the fins. Ich may be caused by poor water quality. You can rid the tank of Ich, but it must be done quickly before it infects other fish. A medication to treat the water can be purchased at most pet supply stores.


• Fin Rot: A fish appears visibly sick, and the fins look to be rotting. This contagious disease is caused by bacteria and occurs when a fish becomes stressed, or due to poor nutrition. To treat it, check water levels and purchase an antibiotic at the pet supply store.


• Cotton Wool or Fish Fungus: This disease will appear as cotton growths on the body, mouth or fins, and it looks like a fungus. It is contagious and usually occurs when a fish is stressed. It is caused by bacteria and also results from low water quality. Cotton Wool can be treated with medication. Regular water changes and tank maintenance prevent fish from getting it.


• Ammonia Poisoning: Fish affected by ammonia poisoning will have red gills and gasp for air at the water's surface. Ammonia levels are high in fish tanks when organic waste develops, or when tanks are overpopulated. To prevent this disease, treat water with an ammonia treatment, ensure that your filtration system is operating efficiently and change water on a regular basis.

Effective Treatment

• There are resources on the Internet helpful for treating fish diseases.


• The best way to keep your fish healthy is regular tank maintenance and providing good nutrition for your fish.


• To treat many of the bacterial illnesses above, a salt bath can be effective. Salt helps fight bacteria and parasites and increase a fish’s chance of survival.


• A salt bath can be made by mixing four tablespoons of aquarium salt with one gallon of aquarium water in a bucket. Completely dissolve the salt and place the fish in the saltwater for about five to thirty minutes. Keep an eye on the fish, and if it seems distressed, take it out and place it back in the fish tank.