I just read through the Dr Motes' paragraphs addressing somewhat higher Phosphorus contents in Florida's water, coupled with alkaline pH.
It makes sense that you don't need to add as much Phosphorus if it is present already.
(Fair Lawn doesn't list any, I just checked )
Normally in acidic water you would have H3PO4, but depending on the alkalinity in Florida water you would have one, two or all three Hydrogens ionized, replaced by Mg.
So, for Florida's water this makes sense.
