Here is a limnological approach. First we should find out what features are causing the depletion of DO? Is it due mostly to accumulations of windblown organic inputs allochthonously (external) or autochthonously (internally produced) materials. Are there secchi disk or water clarity measurements for this pond? Are there excess fertility issues in this pond? Alum will work primarily for helping to lower phosphorus and reducing the internal organic production from phytoplankton, but not for the reducing DO from decay of external organic sources nor from excessive submerged weed growths.
