Koi and Pond Fish Fungal Disease

There are many water bound organisms within our koi ponds that live in perfect harmony with our koi. Even the organisms that pose a threat to our koi require appropriate conditions before mounting an attack such as the numbers of parasites present, water quality in the koi pond, temperature and the general well being of the koi.

We term such organisms as ‘opportunistic parasites’ it waits in the guise of a friend until the koi is weakened then mounts an attack with potential serious consequences for our koi. Fungal disease can affect all living things; they are multi-cellular organisms and are present in all koi ponds regardless of filteration methods. When we observe fungus on one of our koi we must understand that we are dealing with an opportunistic secondary infection.

An entry portal has been made in the koi mucus before the fungus has attacked, what we must do first is find out what has caused the portal. The fungus invades the wound and uses the koi mucus as a source of nourishment and reproduction. The most common fungus that we see in our koi ponds as called saprolegnia on the koi gills and body.

Saprolegnia can appear as yellow tinged cotton wool tuffs, the yellow colour is caused by matter in the water that becomes trapped on the fungus. A small patch of fungus will grow very quickly so it is important that we treat the infected fish immediately.

We must first find the cause of the fungus something has punctured the mucus that has allowed the fungus to gain entry usually this is a parasite. If you observe fungus on just one koi and the other fish seem happy and unaffected then it is possible that the Koi has injured itself on something sharp in the pond and isolated treatment will suffice. Poor water quality can impair the effectiveness of the fish’s protective layer making the koi more prone to fungal infection.

Source by Charlie Knowles