If it was me I would try to get my hands on 50#s of alum and 100#'s of hydrated lime then 20#'s of sodium bicarbonate. Mix the alum and lime together in a bucket then pump or throw it into the pond. With good aeration current it will push it though out the pond in an afternoon.
Mixing Alum and Hydrated Lime together creates a nasty, thick pudding that will not spray at all, and will also not mix into the water column...Create slurries, and spray the two chemicals seperately...
