How do chemical algaecides cause long-term problems?
By killing off ALL algae and most beneficial bacteria, chemical algaecides put additional nutrients (degradable dead algae) back into a water column. Small fish and protozoa, which rely on algae as a food source, die off, leading to death of larger fish, when their food source is killed off. These dead fish add to the climbing nutrient levels, which are not degraded by the now depleted supply of beneficial bacteria, causing an increasingly out-of-balance ecosystem. This unbalanced system supports a growing population of aquatic weeds and more algae until the situation becomes worse than it was prior to the use of biocides. The dead fish, algae, and plant matter sink to the bottom, contributing to the sludge layer, which emits hydrogen sulphide and methane gases as obligate anaerobes take up residence, protected from further biocide use by the amount of sludge at the bottom. Without algae to add oxygen in the day, or beneficial bacteria to alter this cycle, the pond changes from aerobic
