Liming materials may contribute substantially to fish yields by
improving conditions for fish, and by enhancing the primary
productivity of the pond. Alum is an effective flocculant for
reducing clay turbidity. Gypsum is less useful in this regard,
but is better suited to raising hardness than lime or alum because
of its greater solubility. Potassium permanganate is a useful
disinfectant, but may actually be detrimental if added to ponds
suffering from oxygen depletion.