Diseases that Attack Pond Fish
Most diseases only attack fish in a weakened condition, and can be averted by simple husbandry. Most diseases occur in spring when the fish are coming out of their inactive period with reduced resistance, or in the autumn because they have not been properly treated during the summer.
It is important to build up energy reserves from midsummer onwards. Besides using good quality fish foods, a lump of cooked porridge, as much as can be consumed in 15 minutes, is beneficial. If the pond is cleaned at the end of the season and is deep enough for the fish to avoid the ice, disease-resistance should be high.
This is one of the most common problems. It is caused by Saprolegnia, a fungus which produces tufts of long (usually white) fibres attached to the fish. Physically damaged or weakened fishes are particularly prone to infection. Treatment using a proprietary remedy is effective and can be carried out either in the pool or in a tank.
Sometimes a fish appears to have been attacked by other fishes, with its tail and fins ragged. This may be the result of a bacterial infection that slowly disintegrates the fins, leaving only tattered fin rays. The disease starts at the extremities and gradually spreads towards the body. It is usually prevalent in long-finned coldwater fishes when the water temperature has been consistently below 10°C (50°F). Effective cures are available, but prevention lies in the hands of the fishkeeper.
This is one of the most intractable conditions and is believed to be brought on mainly by stress. Ulcerated patches appear on the fish’s body, as if the flesh had been eaten away. It is best overcome by maintaining clean conditions. Try proprietary remedies and painting the ulcers with Friar’s Balsam.
This common parasitic affliction, caused by a protozoon, shows as small white spots all over the fins and body. It should not be confused with the white tubercles that appear on the gills and pectoral fins of male Goldfishes in the breeding season. Proprietary remedies are effective.
Occasionally a fish has its scales projecting, with an overall bloated look and protruding eyes. This condition, dropsy, is a rare disease for which there is no known cure; lift the fish out and destroy it.