Hosty - From what I have read about the information on the new herbicide Habitat by BASF, it looks to be the best choice for your friend to reduce the infestation of "water lilies" in the 1/4 acre pond. Good control with minimal concentration of chemical into the pond. This chemical has a short life span and low residual and very low, if any toxic affect on animals including invertebrates. Treatment time will, in my opnion, be best in July or August when the lilies are manufacturing food reserves and sending materials to the roots.
