Some fish diseases are common and others are rare but knowing their characteristics is helpful in the prevention and cure.

Disease can break out in a fish tank very quickly and you have to first identify the type of disease before you can take action. Within a disease group, there are different symptoms and that can make identification even more difficult. This article will explain five disease groups and how fish are affected.

Bacterial Disease in Fish

The bacteria are transmitted by fish having made contact with other diseased fish. Bacterial fish diseases and infections are very common and are one of the most difficult health problems to deal with. Bacteria can enter the fish’s body through the gills or skin or it can stay on the surface of the fish’s body.

There are four types of bacterial infections:

• Bacterial gill disease –the gills are the primary target
• Systemic bacterial disease – bacteria invades the fish’s body and damages internal organs
• Bacterial body ulcers – lesions on the fish’s body that can be shallow or deep
• Fin rot – most likely resulting from environmental stress

There are several reasons why fish can become stressed. The most common reasons are poor water quality, parasites, overcrowding the tank or sudden changes in temperature

Fungal Diseases in Fish

This disease is caused by various groups of aquatic fungi. Fish will develop white, grey or brown cotton-like growths on their skin, gills or fins. Fish will develop breathing problems if the growths are on the gills. There are always fungal spores in an aquarium. An outbreak will occur on a fish that has scraped or damaged its skin or gills.

Non-Infectious Fish Diseases

Non-infectious diseases can be caused by simple things such as environmental, nutritional, or genetic situations. Other causes can be low oxygen or high ammonia levels, plus many more natural causes.

The three categories: environmental, nutritional, and genetic.

• Environmental diseases - include high ammonia, high nitrite, low oxygen or toxins in the aquarium.
• Nutritional diseases - can be difficult to identify. It is usually due to a lack of vitamins, such as vitamin C.
• Genetic abnormalities - can be present in any fish, such as lack of a tail or an extra tail.

Viral Diseases in Fish

Viruses are small infections that multiply within the cells of a fish. They are very difficult to detect because they are small. As the infection progresses, the fish will darken and the eyes will bulge with traces of bleeding around the eye. The gills will grow pale and may bleed. Because of the bleeding, the fish will become oxygen deprived. These are one of the more common diseases found in aquariums.

Protozoan Fish Diseases

These are other common diseases found in the aquarium.

Here are some examples:

• Velvet or Rust – the fish develops clamped fins, difficulty in breathing and yellow or light brown dust on the fish’s body
• Costia – characterized by milky cloudiness on skin
• Hexamita- the fish’s feces is slimy and white
• Ich (Ichthyphthirious) – these are salt-like specks on the body and fins accompanied by excessive slime. The fish has breathing problems, clamped fins, and loss of appetite.

General Prevention of Fish Disease

To reduce the risk of disease, be sure to do the following:

• Clean the filter on a regular basis
• Don’t over feed your fish
• Keep the chemical levels stabilized
• Maintain a steady water temperature
• Don’t overcrowd your tank

Hospital Tanks

If only some of the fish in your aquarium are sick, you can isolate the diseased ones in a hospital tank. Buy a cheap aquarium and keep it on hand for administering medication. After the fish are put back into their aquarium, be sure to clean the tank thoroughly.