The power of the heat test
If you do not do a heat test for PO4 you will not know what your value truly is, this is so important and leads people to think algae issues are not PO4 related as they see a zero value. As the above shows, unless you do a heat test you are not getting the true and accurate value.
Ok so carry on as planned using the Ultra power phos to the instructed amount for 7 -14 days or until you get zero reading under heat test conditions.