 Sludge accumulation in a pond occurs for a variety of reasons. Leaves and grass clippings can be blown into the pond. Droppings from animals such as fish, ducks, or geese can sometimes be significant. Even over-feeding the fish in the pond can promote sludge accumulation. In many ponds, the largest contributor to sludge build up is dead algae. Every year, algae populations increase to at least some extent during the warm sunny months. These algae die off, and then become part of the sludge accumulation.
Sludge build-up causes four significant problems. First, it results in an anaerobic zone (meaning a zone without significant dissolved oxygen). An anaerobic zone is a place where potentially dangerous, disease-causing bacteria (pathogens) tend to grow. The larger the anaerobic zone (meaning the greater the depth of sludge build up), the greater the potential for significant populations of pathogenic bacteria in the pond, which can harm fish.
Second, sludge build-up is the main cause of pond odors. When the build-up is significant, hydrogen sulfide (which has a rotten egg odor) is produced. And hydrogen sulfide is not only odorous, but can poison fish.
Third, sludge build-up may deplete oxygen reserves, particularly during warm weather. The worse the build-up, the worse the oxygen depletion. Of course, low oxygen levels can be stressful or even fatal to fish or other wildlife.
Fourth, as sludge build-up reaches excessive levels, nitrogen and phosphorous that is part of the sludge will slowly be released. This nutrient release can cause severe water quality problems, including algae blooms. |
