If I put koi in my pond or water garden, will they eat all the algae and keep the pond clean?
This myth is fairly common and seems to stem from the fact that ‘grass carp’ are known to feed on plant material including algae. While koi (and goldfish to some extent) will feed on certain types of algae, they will not eliminate algae from a pond. Furthermore, the introduction of fish (or adding too many fish) into a pond or water garden that is not capable of supporting them may cause more problems in the long run, including overloading the bio filter which may produce a green water situation.
