Copper is a potent biocide that is effective in controlling the growth of microbial organisms in pond water, even at low concentrations. Copper ions bind to proteins in algae, destroying cell walls and inhibiting photosynthesis.
How to Use Copper in Ponds
There are various ways to use copper to control algae, including copper algaecides, pond ionizers, and even copper water features like spitters and statues. If you are treating a larger pond that does not contain trout, grass carp, koi, or goldfish, Airmax Algae Defense provides fast-acting algae control.
Copper algaecides are highly effective in large ponds and lakes but are too strong for water gardens. They can disrupt the delicate balance of small waterbodies and incidentally harm aquatic invertebrates and sensitive fish. Furthermore, some algaecides can deteriorate pond liners, leading to catastrophic leaks.
To harness the algaecidal properties of copper in your small pond, you can use a pond ionizer to slowly release copper ions into the water at safe concentrations. For the best results, combine a pond ionizer with an EPA-registered copper-free algaecide for water gardens.
Will Copper Sulfate Kill Fish?
Copper algaecides come in two main types: copper sulfate and chelated copper. We recommend only using chelated copper algaecide in larger ponds to prevent an overaccumulation of copper, which could harm your fish.
Copper sulfate rapidly sinks to the pond bottom, where it accumulates in sediment, leading to dangerously high concentrations of copper that can only be remediated by dredging and performing significant water changes. Furthermore, the National Pesticide Information Center states that copper sulfate is highly toxic to fish and aquatic life, especially trout, koi, and the fry of many other fish species.
Conversely, chelated copper algaecides stay suspended in the water column longer, allowing for a controlled release of copper ions. This is more effective for controlling algae and requires lower and fewer doses, making it easier to avoid dangerous copper concentrations.
Learn More About Pond Algae Control
If you are struggling with pond algae overgrowth and don’t know where to start, contact us online or call 866-POND-HELP. Our experienced pond experts can help you identify the types of algae plaguing your pond and provide personalized treatment advice.
Read more algae control tips in the following related guides:
Pond Algae Control: Remove & Prevent Blooms
Types of Algae in a Water Garden
Last Updated: May 29, 2025