Phosphorous(P) is a naturally occurring element that is valuable to the residents of a pond food chain. When phosphorous is limited the productivity of primary consumers and producers is reduced. On the other hand, when phosphorous is too abundant overproduction of aquatic plants and some animals can happen with the result being an ecosystem that is out of balance (eutrophication).  The majority of man-made ponds have a limited amount of naturally occurring phosphorous in the water.  The problem most pond owners experience is when this nutrient enters the water from an external source and is rapidly absorbed by aquatic plants producing green water conditions. These are some sources of phosphorous that exist outside of the pond (non-point sources):

  • Stream or creek water that contains suspended soil particles
  • Grass clippings from lawn equipment
  • Lawn or landscape fertilizer
  • Deciduous leaves
  • Residential waterfowl
  • Septic tank overflow

There are several internal sources of phosphorous that are contributed to the aquatic ecosystem:

  • Decaying macrophytes (submerged aquatic plants)
  • Soil sediments
  • Fish
  • Microbes that digest organic bottom sediments

These are a few suggestions for reducing (P) from influencing the balance of your pond:

  • Avoid stirring up the bottom soils that act as a phosphorous sink. Bottom feeding fish will stir up soil sediments
  • Divert or reduce water flowing from a stream or from uncontrolled sources from entering your pond
  • Maintain 40% or more aquatic plant growth on the bottom of the pond to uptake nutrients
  • Use grass carp carefully and remove them when macrophyte growth is less than 40%
  • Avoid the use of aquatic chemicals to keep your pond from becoming a science experiment
  • Mechanically remove leaves or digest them with probiotic bacteria
  • Permit cattails to grow and uptake phosphorous then harvest the expired plant material during winter

If you are using your pond for recreational enjoyment clean clear water is appreciated, but if you are trying to produce big catchable fish, green planktonic water is preferred and very productive. Maintaining a healthy pond is quite simple if you reduce the phosphorous that enters the water from external sources and monitor the accumulation of organic matter that settles to the bottom.