Good point!
Although we just talking PO4 here I list all my test kits for reference.
Alk, Hanna
PO4, Hanna http://hannainst.com/usa/prods2.cfm?...01&ProdCode=HI 96713
Cal Pro, Red Sea
Mag Pro, Red Sea
K Pro, Red Sea and Korallen-zucht (zeo)
FYI, I send my water off every month to...