How should I clean my pond? When should I clean my pond?
Some ponds are never cleaned and the ponds and its occupants survive very well. However, a large number of ponds are created with high fish densities or are built in locations were the pond receives a great deal of debris over the year. Even if you start out with just a few fish initially, in a healthy pond they will breed to the point that the number of fish will push the environmental limits of your pond and biofilter. The debris may be the result of leaves blowing into the pond, the die-back of vegetative pond plants as well as fish wastes. It is these latter types of conditions that will necessitate you cleaning the pond eventually. The two most likely time points for cleaning are in the fall, to reduce the amount of accumulated muck on the bottom of the pond as you head into winter, or in the spring to remove material accumulated over the winter from leaves blowing into the pond, accumulated fish waste or catkins and similar materials shed by trees as they leaf out. Cleaning in the fall reduces wastes in the bottom of the pond which may turn anaerobic if sufficient oxygen is not available, creating a breeding ground for harmful bacteria, or which may decompose, releasing ammonia and other dangerous chemicals that can be trapped under the ice. The build-up of these pollutants can lead to fish kills over the winter months. While keeping a hole in the ice over winter will help alleviate the accumulation of gases, cleaning the pond before winter sets in will reduce the overall potential for problems. Cleaning the pond in the spring may help reduce diseases and parasites that often occur as the pond and its biology warms up for the summer, as well as reduce the overall availability of nutrients that stimulate algae growth. The following are a few approaches that have been successfully used to clean the pond.
1. If the pond has a bottom drain periodic changes of water (typically 10% per week) have been used to evacuate the accumulated debris from the bottom of the pond. This simple approach minimizes the amount of material that is removed at any one time as well as adds water to the pond on a periodic basis. Care must be taken when adding water to be sure that you have minimized the addition of chlorine and chloramines typically present in many municipal water supplies. This can be done either by pre-treating the water with dechlorination agents or by using a whole-house water filter with an activated carbon cartridge.
2. Using a net such as used in swimming pools is helpful for cleaning out large materials that have settled to the bottom of the pond. However, if there is a very large amount of debris in the pond you should be careful to either remove the fish or use supplemental aeration to avoid creating significant oxygen deprivation due to stirring up anaerobic or large amounts of oxygen-consuming muck. If you notice a rotten egg smell this indicates the presence of hydrogen sulfide. You should immediately stop stirring...