Algae Problems in Water Gardens Algae problems in water gardens are generally caused by the action of the sun and excess nutrients in pond water. If ponds are established properly and are properly balanced with the correct ratios of plants, fish and scavengers, algae control and algae problems are not difficult. When first establishing a water garden, a green water condition will exist for approximately three weeks but will clear as the water equalizes between plant nutrient uptake and the introduction of nutrients from fish. The general cause of algae in ponds is excess nutrients from either the overstocking and overfeeding of fish, or the lack of nutrient uptake by plants caused by planting too few plants in a pond. Feed fish a specified amount of food per day, and only if necessary.
Most fish can thrive on naturally occurring foods within balanced garden ponds.
General methods for reducing algae in ponds include the reduction of nutrients causing the algae problems. To reduce nutrients, reduce the feeding of the fish, the level of fish stocked in the ponds or the fertilization of aquatic plants. The final and most radical method of controlling algae in ponds is an application of an EPA-approved aquatic herbicide. The aquatic herbicide of choice would be a copper compound. At certain levels in low alkalinity water, copper compounds can be toxic to fish and to plants.