Every pond does not need to be fertilized as many outside the south have more than enough natural fertility to produce a good plankton bloom without help. The danger with fertilizing a naturally productive pond is you achieve to dense a bloom that uses up all the DO at night and causes a fish kill. There are many naturally fertile northern ponds where fertilization will not reduce FA because it grows in colder water before the fertilizer can work. In those ponds FA will grow before the plankton bloom which will then occur when its time and other methods of FA control have to be used , if the pond owner wishes to do so.