Common Pond Problems
Greenwater
Unlike lakes and rivers, ornamental garden ponds are generally of small size with limited depth. Therefore they can warm up more quickly than natural bodies of water; they also have greater sunlight penetration and a higher concentration of nutrients. These conditions stimulate the growth of algae, which cause greenwater problems. These conditions can be reduced by maximising pond volume, minimising stocking levels, placement of pond away from direct sunlight, or blocking sunlight using canopies or pergolas, not overfeeding fish, and using correct food ie wheatgerm during cold periods. The best way of preventing greenwater after taking all these considerations into account will be to utilise the correctly rated pump, filter and UVC. Pollution Caused by Fish Waste
Compared with natural ponds, garden ponds are usually heavily stocked with fish, which are fed more than they would normally find to eat in their natural habitat. Fish produce waste in proportion to the amount of food eaten. This waste is both solid and dissolved; this pollution is increased by the decomposition of plants and uneaten food. If these waste products are not removed they will eventually have a detrimental effect on your fish. Filtration is the key here, your filter should be large enough to cope with the demand placed upon it, if you wish to have large stocking levels, and you are intending to feed large amounts of high protein food in order to grow your fish to impressive sizes, then purchase a large efficient filter that can cope with these demands. Closely monitor your fishes behaviour, watch for anything unusual, this will be a sign that things are not as they should be, follow the pond feeding guidelines on this website, and remove any uneaten food or decomposing plant matter.
Herons
Herons are the number one enemy of fish ponds. Besides catching and eating healthy fish, they injure others which die later. They are most troublesome in spring when they have young to feed, not in winter. They are no longer fooled by fake “decoy” herons. Deter them by putting a trip-wire around the pond or using an electric heron alert, or cover the pond with a net. Herons are less of a problem in towns or where a pond is close to tall fences, a shed or a greenhouse, as they need a long, shallow flight path before landing.
Lack of Oxygen
Both green water and pollution can reduce the level of oxygen in pondwater. However, relatively high concentrations of oxygen are necessary to support healthy fish. The introduction of air into pondwater i.e. aeration, raises and stabilises the level of oxygen in the water. In addition the turbulence created by aeration will remove toxic gases. During the summer months when water temperatures rise lack of oxygen can become a problem, suspect this if you see your fish gasping at the surface.