Pond Boss Forums MANAGING AN EXISTING POND Fertilization Serious Ammonia problem

Firstly are you sure that your ammonia test kit is accurate? Does water from another normal pond test normal for ammonia? If so then your test kit is probably fairly accurate.
High concentrations of ammonia could be coming from lots of bacteria decomposing organics. Although as you mention a dense phytoplankton bloom should be utilizing lots of the ammonia.