Salinity is pretty high at 1.028 , I would buy a Salifert nitrate test to get a better idea where it's at for sure. If the nitrates are truly 0 then your LPS are not going to be happy , and as someone already mentioned will make your tank no3 limited and not allow bacteria to consume po4.
I also agree with investing in an rodi system. How often does the film algae regrow on the glass after cleaning ?
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