Algae in Fish Ponds
Algae can grow excessively if a fish pond receives too much sunlight and/or if there are too many nutrients in the water. There are two types of algae treatments. One that is suitable for fish ponds containing live plants, the other for fish ponds (or water features) which do not have live plants. The first treatment works by restricting the availability of nutrients to the algae. This treatment, Algaefix, is an effective algae treatment that is safe to use in fish ponds containing live plants. The second type of treatment uses copper as an algaecide (algae killer). This is safe to use with most fish, but is toxic to live plants.
If a fish pond receives more than a few hours of direct sunlight, especially in summer, some algae growth can be expected. If the fish pond receives more than half a day's sunlight, significantly more algae growth can be expected. There are a few ways to reduce sun exposure. Having a fish pond on the east-side of a house can provide morning sun and afternoon shade. Water lilies and other surface-shading aquatic plants can help block sunlight, together with plantings on the north-side of a fish pond in Australia. Shade-cloth with a 30-50% sun-blocking factor can be used, depending on your location and the season. Generally 30% shade is best for winter and 50% shade is best for summer.
As fish food is added to a fish pond and fallen leaves accumulate on the bottom of a fish pond, they provide nutrients to algae. Pondzyme is a product which can help reduce this sludge and decrease algae growth. There is a certain amount of phosphate in fish food and this phosphate is the main contributor to excessive algae growth. Adding more live plants to a fish pond, particularly underwater plants, can help reduce algae growth by absorbing these excess nutrients. If a thick layer of sludge accumulates on the bottom of a fish pond, this sludge will continue to release nutrients into the fish pond. Regular removal of this sludge will help reduce the likelihood of excess algae growth.