Can you trap him out for a while? Put him in the QT for a few weeks and
let the shrimp settle. in.

I had problems with my pseudochromis, I took a 20 ox coke bottle and cut
the neck off of it and inverted it into the bottle (make sure you cut the
cap threads off) and secured it with a staple. After 3 days of not
feeding him, I placed some flakes in the bottle and dropped it in the
tank so it lands on it's side. After a minute or so, the pseudo swam in
there, and he was caught. Into the QT he went.