killer clown!

just added 2 more(3 total)royal grammas to my 210 reef. i've got a sebae clown fish, that totally attacks one of the grammas. he bit off almost the whole back fin!!! why is this?

 

did the gramma get to close to the clowns home? they get mean if they are hosting in anything be-it an anemone or a pot

 

no, thats the thing, the clowns anemone is at the far left of the tank. the rock where the grammas hang is at the far right of the tank.totally opposite sides. yet, when he sees the grammas, he shoots to the other side of the tank to go after them!i'm not sure if the one he bit up is just a weakling, but the others just shoot into the holes in thier rock.
think i should remove the one he attacks? i don't want to see him killed.

 

its his territory.change the rocks around and quarantine the lil guy till he gets better

 

he's got his hiding spot, now. seems to be doing ok.
since i've got 3 royal gramma, and the other 2 have paired off, should i buy another in the hopes that it buddies up with "stumpy"? feel bad for the little guy. seems like everyone's got a friend, but him.