I have to be honest, I have some dark stones, like little mirrors, that every once in a while my fishy's do notice themselves in, and they start having an arguement with themselves, but for the most part Honestly..they actually get used to it, they look every now and again, but don't stare, How long have you had the tank, if it's new~then it maybe just the fishy getting used to seeing himself, after he sees himself more often, he may be ok, unless you see a lot of flaring, just staring is not bad.