There are a number of parasitic organisms which are present in the pond environment. If good water conditions are maintained and the fish are healthy and unstressed, these parasites will rarely cause a problem. If the fish’s immunity levels drop due to causes of stress, or if the pond is too heavily stocked the parasites can become problematic.

The common symptoms associated with a parasitic outbreak are;

• Flashing – the fish will flick or flash its sides in an attempt to remove irritating parasites.

• Slime Disease – slime disease is an over-production of the fish mucus layer. This is due to constant irritation of the skin which can be caused by parasites, but can also be due to poor water conditions or fine particles in the water. The mucus builds up to look grey or white in colour and sometimes appears to drape off the fish. A heavy build up of slime can coat the gills and, in some cases, suffocate the fish.

• High respiratory rate – some parasites attach to the fish’s gills, starving the fish of oxygen. The fish reacts by gasping for air at the surface of the water, especially under fountains and waterfalls where the water contains more oxygen. Fish may also gasp for air if there is very little oxygen dissolved in the pond water.

Many of the parasites are visible and can be seen on the fish’s body. Some of the more common parasites found are;

• White spot – visible as white spots about the size of grains of salt which form all over a fish’s body.

• Anchor Worm – can be seen as barbs protruding from the fish’s flesh. Anchor worm can be removed with tweezers, but this has to be done very carefully as the head of the worm may break off which may lead to further infection.

• Fish Lice – Lice are visible as small brown/translucent lice which roam around the fish’s body.

When treating a parasitic outbreak the pond should be partially water changed and any build up of sludge or debris on the bottom of the pond or in the filter, needs to be vacuumed or cleaned out. The whole pond should be treated with an anti-parasite treatment.Care should be taken when buying new fish, and any natural décor used around the pond, such as rocks or wood, should be thoroughly cleaned before been added.