This is Harry. Harry is an arsehole
Sorry, nothing much of value to add, but that did make me chuckle.
All I can suggest is moving the rock it's on. My clown was hosted by one of my torches for a couple of days, and when I rotated the rock a little, he lost interest in it. Not sure it would have killed the torch, but it was definitely retracted.
And as to why they suddenly notice it? Who knows. I'm not sure they're the smartest fish TBH. For example, after going mental for it for months, mine now completely ignores mysis but I noticed him the other night chasing down and trying to eat a big turd one of the other fish did.