The Mystery of the Rotten Egg Reek

By Dr. Josette La Hée, Senior Environmental Research Consultantpond odors stink

Step outside to take a breath of fresh air…and gag! Your pond has decided to get your attention in the most effective way it can. A bad odor coming from your pond is always a sign of something being out of whack. The odor can range from a strong earthy smell or pungent sewage stench to the wonderfully rich whiffs of a rotting carcass. Ah nature…

Whatever the smell, it is usually possible to diagnose and treat your pond’s condition. In this blog entry we will investigate The Mysteries of Pond Odors and learn all about the fascinating ways in which your pond can become smelly. So let’s go!

Why does it stink?

That gag inducing, rotten egg smell emanating from your pond is the result of a very simple equation:

Low Oxygen + Plenty of Anaerobic Bacteria + Lots of Organic Matter  = Hydrogen Sulfide
(aka rotten egg odor)

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).

If there is a good amount of oxygen in your pond, then the oxygen-needing aerobic bacteria will happily breakdown organic matter without releasing hydrogen sulfide.

If there is very little oxygen in your pond, the non-oxygen-needing anaerobic bacteria will step in and breakdown the organic material. But, as they do it, they will give off hydrogen sulfide and produce that rotten egg smell. So, the only way to get rid of that odor is to alter that equation:

Lots of Oxygen + Aerobic Bacteria +  Little Organic Matter = No Hydrogen Sulfide (no odor)

How do we change the equation?

  1. Raise oxygen levels
  2. Increase aerobic bacteria
  3. Decrease organic matter

We’ll go deeper into each of these in the next chapters. For now, if you are experiencing bad odors, contact us for an evaluation of the cause and steps to improve it.

About Dr. Josette La Hée, Senior Environmental Research Consultant

Dr. 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.