Substituting fish would the problem probably solved, but their "catchment" planned for next spring.
So we took up NEUDORFF-free mosquitoes back, dilute 9 ml of the active solution with 10 liters of water and distributed them evenly in the garden pond.
The very next day the larvae were dead and drove to the surface. Other insects like water striders or beetle cavorted still alive in or around the pond. Also at the water plant, I can not detect any impairment.
