I have a large amount of string algae on the rock of my waterfall. Can’t see any in the main part of the pond. Didn’t have this problem in the warm weather. Started about a month ago. Should I treat this problem in the winter months (Feb.)? Will it damage Koi?
Treatment is fine, just make sure the “treatment” is safe for the Koi and will work in the cold temperature. Most water treatments are plant and fish save.