Foam on Koi Pond: Causes and Fix

Clean, filtered koi pond has foam. Asks cause.

Foam = Organic Overload

Dissolved organic compounds (DOC) from fish slime, waste, spawning, excess food, rotting plants.

Fix

1. Reduce feeding.
2. Add beneficial bacteria.
3. Foam should diminish in 1–2 weeks.

Water changes and activated carbon also help.