My newest boy Chicory flared at himself in the mirror behind where I had his tank originally - so much so that I finally put a book between his tank and the mirror. Since then, I haven't seen him flare till just a little while ago. I can lean close to the tank and he comes forward, and then will follow my hand and dance. But when I held a pen up for him to inspect, he flared at it bigtime.
A pen ~.^
Just see what yours likes to interact with?