Fish fungal disease is caused by water molds

Signs of infection The obvious sign of infection is cotton-wool-like growths, usually white, but sometimes grayish black to green. The fungus usually starts on the body and trunk, but it may also originate at a site with some injury, and it can spread to attack the fins, mouth, eyes and gills.

Affected fish All fish may be harmed.

Details of infection Fungi are plants that grow on dead organic matter. The typical fungal body, or mycelium, is made up of very fine filaments or external hyphae, and the external hyphae pierce dead or decaying tissue and absorb nutrients directly through their cell walls. Therefore, although fungal spores are present in the water, healthy fish can resist infection. Spores are released from the swollen tips of certain external hyphae and swim freely by means of two flagella until they settle on suitable tissue and begin to grow into another fungal mass. Fungi attack only fish that are already injured, or fish that are weak in some way. If an attack appears to occur spontaneously, it may be a secondary infection of tissue damaged by other causes, such as damage by skin flukes. In these cases, both the fungus and the primary infection need treatment; if untreated, the fungus can die. Damaged or unfertilized eggs are especially susceptible to fungal attack, while healthy eggs in the same batch of eggs laid can hatch normally. It is often wise to remove eggs with fungal growths in order to protect healthy eggs from being held back in their development.

Recommended treatments In an aquarium, possible infection can be prevented by checking whether the water is in good condition, whether the water is at a suitable temperature, and whether the water is not too alkaline (for a freshwater aquarium, the best is PH7.2). Many treatments are recommended for use, but some of them have serious disadvantages. A salt bath is a traditional treatment for freshwater fish diseases, but it causes undue irritation, requires frequent changes of method, and is not particularly effective when used alone. Methylene blue is effective for mild cases, but the prescribed dose colors the water, making it difficult to continuously check the progress of the disease. Malachite green can be applied to the infected area, and there are several new specialized treatments, which are generally effective against fungi.

In ponds, fungi usually appear in spring, when fish are weakest, or after spawning when they have become damaged. Before damp or cold weather begins, feed the fish a balanced and nutritious bait to "fatten them up" (lumpy boiled porridge is suitable as a fattening bait), and ensure that the water PH is satisfactory (between PH6.5 and PH7.8). This may reduce the plan for fungal infection. There are already specialized fungal treatments for use in ponds. However, depending on environmental conditions, it is best to move infected fish to a suitable container where more stable conditions can be maintained for treatment. Great differences in heat and cold can reduce the effectiveness of drug treatment and promote further infection. For example, when doing the old-style bath, be sure to carefully move the fish to a large container filled with chlorinated water or aged water, and ideally oxygenate the water. Avoid causing undue irritation to the fish at all costs. When moving the fish, wipe off the fungal growths on the fish body with cotton wool.