I've had plenty of BTAs over the years decide to do a walkabout and start killing tankmates. 
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Currently, there is a Sally Lightfoot that has outgrown its welcome and has killed my smaller fish. Playing chase around the coral/rocks has not resulted in his expulsion: I’m working on a bottle crab trap which will probably catch all my hermits. Sigh….
I wish my mantis would enter the dang bottle trap!LOL...I just made a bottle trap for 2 pesky peppermint shrimps last night. Aside from catching the 2 shrimps, I wound up catching every bumble bee snail in the tank. I would have caught a few trochus as well but they couldn't make it through the hole. Bottle traps are great for catching cleanup crew.