Eliminating the Rotten Egg Reek – Organic Matter

In parts one and two, we learned the major causes of the awful odor and bacteria’s role in it. Today, we will discuss how events outside of the water affect the bottom of your lake. To recap, the rotten egg smell emanating from your pond is the result of a very simple equation: Bacteria + Lots of Organic Matter + Little Oxygen = Hydrogen Sulfide (aka rotten egg odor)

Any organic matter that gets into your pond (e.g. leaves, grass cuttings, dead plants, etc.) will get broken down by bacteria. There are two types of bacteria: ones that need oxygen ( aerobic ) and ones that don’t ( anaerobic ). Bacteria + Little Organic Matter + Lots of Oxygen = No Hydrogen Sulfide (no odor)

Bottom muck starts at the surface

pond organic matter

That mushy muck you find at the bottom or edge of your pond is what you end up with when bacteria breakdown organic matter. That organic matter can be leaves, dead algae, dead plants, dead fish, etc. You can reduce the amount of organic matter entering your pond, and thus the amount of organic matter available for the bacteria to breakdown, by doing such things as:

  • Keep trees trimmed and away from the edge of the lake
  • Rake up leaves and grass cuttings before they get in the water
  • Clear away dead plants floating in the water
  • Remove dead fish from the water

This can help significantly, but keep in mind that many ponds already have a lot of organic matter sitting in the sediment. Also, it is extremely difficult to stop certain other organic inputs. Think about the fine organic matter in storm water inflows, or the surprisingly large amount of excrement (poop) that can enter your pond from fish and birds (Oh those Muscovy ducks!).


  • Cutting down the amount of organic material entering your pond can lessen the activity of anaerobic bacteria, which in turn will reduce the production of hydrogen sulfide odor.
  • Educating yourself and residents on the impact they have and the simple things they can do to help is a good step towards having and maintaining an odor-free lake.

The Rotten Egg Reek mystery has been solved!

For help with pond odor problems, contact Aquatic Systems Today

About Dr. Josette La Hée, Senior Environmental Research Consultant

Josette La HeeDr. La Hée conducts research for Aquatic Systems on urban aquatic ecology. The primary focus of her research is the use of sustainable management techniques for restoring impaired lakes and ponds. As Head of Limnological Research, Dr. La Hée spent three years working with biologists in our field offices. She designed and ran lake aeration studies on multiple lakes throughout Florida. Additionally, she developed the lake assessment and monitoring protocols used in our lake management programs. In addition to research, Dr. La Hée conducts teaching and training sessions for lake management groups.  She has presented research at conferences including the North America Lake Management Society and the Florida Aquatic Plant Management Society.