Foam on the surface of a koi pond can be caused by koi spawning (reproduction). During spawning, koi release eggs, sperm, and proteins into the water. These organic substances mix with air from waterfalls and water circulation, producing white foam.
Spawning-related foam is generally temporary, but the additional organic material can affect pond water quality.
Signs your koi are spawning
- Male koi actively chase female koi around the pond.
- Fish splash or swim rapidly near rocks, plants, and shallow areas.
- White foam suddenly appears on the pond surface.
- Small, sticky eggs may be visible on underwater surfaces.
How to remove foam after koi spawning
- Remove excess foam: Skim accumulated foam from the pond surface.
- Maintain filtration: Keep the pond pump and filtration system operating normally.
- Remove organic waste: Clear excess debris and unfertilized eggs that may decompose.
- Check water quality: Test ammonia and nitrite levels following spawning.
- Perform a partial water change if needed: Use properly treated, dechlorinated replacement water.
Aquascape products that can help
- Aquascape Pond Foam Free: Quickly eliminates visible surface foam caused by organic compounds. Safe for fish and aquatic plants when used as directed. Recommended for immediate foam removal.
- Aquascape Activated Pond Carbon: Helps absorb dissolved organic compounds that contribute to foam formation. Place the carbon in the pond's filtration system or an area with good water circulation, following product instructions.
Will the foam disappear on its own?
Yes. Foam caused by koi spawning typically decreases as organic materials are removed or processed by the pond's filtration system.
Aquascape Pond Foam Free can provide faster visible foam removal, while Activated Pond Carbon can help reduce dissolved organics.
If foam persists or fish show signs of distress, test the pond water and investigate possible water-quality problems.