Hydrogen Sulphide in Ponds: What Causes That Rotten-Egg Smell and What It’s Really Telling You
Hydrogen sulphide in ponds is often identified by a strong “rotten-egg” smell and is a clear sign of low oxygen conditions at the pond base. This gas forms when organic waste such as leaves, sludge, and fish debris decomposes in areas where oxygen can no longer reach, allowing anaerobic bacteria to produce hydrogen sulphide as a by-product.
In this guide, AquaFanatics explains what causes hydrogen sulphide in garden ponds, wildlife ponds, koi ponds, and swimming ponds, why it can be harmful to fish, and what the smell is really telling you about your pond’s health. Rather than being a water quality failure, hydrogen sulphide is a symptom of poor circulation, excess organic build-up, and oxygen imbalance.
Learn how to prevent hydrogen sulphide naturally by improving oxygen delivery, managing sludge, and restoring long-term biological balance — without resorting to chemicals or disruptive clean-outs.
