I seem to have struck a nerve with you although that wasn’t my intention. You did however repeatedly mention that OP should drop his PO4 to ZERO. Zero is NOT 0.1 or 0.05 or 0.03.
To clarify zero = 0.
Only now have you decided to backtrack on your reckless advice and instead aim for a good number of less than 0.1, which by my calculations only requires a water change of roughly 6g taking into account sand and rock displacement for water and the internal volume of his tank.
I will continue to stand by disagreeing with that particular post and hey if you want to label me king of reefing, go right ahead

The advice I gave to the OP was to proceed with utmost caution if he were to follow your advice. I think you were reckless to tell a newcomer to aim for zero nutrients. Their reasonable assumption based on your statement would be to aim for 0.00 PO4 and 0.00 NO3.
Point me to a single study where PO4 kills corals, please I beg of you.
You go on to state that he shouldn’t worry about STN because his system isn’t dialed in yet? What does that have to do with anything??? We should all be worried about STN no matter the dialed in state of our tanks. OP has come to this forum because he is concerned for the state of his livestock. As a responsible owner STN is something to worry about and not recklessly introduce.
@James M
Do you have an ICP test on the go yet? If you have some spare cash and the thought of metals is worrying you then maybe consider something like metasorb. It will absorb a few metals, not just copper. Of course until we get an ICP analysis we are kind of guessing.
When doing water changes to lower concentrations of certain elements you should measure the inside of your aquarium and take into account the volume displacement of rocks/sand/coral. Alternatively put everything in a bucket then measure the water you have left. This will serve you greatly later if you decide to dose anything.
Most people will say they have a 20g tank and dose accordingly but most likely you only really have 12-14g. If you go down the route of Lcl or KNO3 then you would be heavily overdosing your tank without realising.
“Nothing good happens quickly in this game”