I wouldn't purposely attempt to raise po4 and no3 until GHA is all gone.
Fish can be stubborn, especially when it comes to their preferred sleeping spot. I know someone who had a Naso Tang that was getting stung every night by a large euphyllia. He couldn't catch the fish and the coral had grown into a large rock that couldn't be removed. He would watch the fish (with a flashlight) every night get stung over & over by the sweepers. The fish kept getting more and more marks all over it's body, and one day he found it dead.It's a torch. I'll try to find him.
Will he eventually learn?