the ULR hanna still reads 0.90 even when i dilute the sample to be test 8mls rodo and 2mls tank water..ugh!!The acrylic tank is not ruined. It may need to have precipitate cleaned from it, if it is clouded with solids.
I'm not sure how much phosphate to expect to still be in the water as a lot likely precipitated as magnesium and calcium phosphate, independent of the Seakler additions.