EVERYTHING sets my Jag off. He's been an ornery sob since birth. While a juvie, he pushed his brothers and sisters around. Then after pairing off, he would be ridiculously aggressive during spawning. He eventually turned on his mate, killing her. His aggression did not subside after being left alone, however. He flares and glass bangs at everyone, and goes COMPLETELY nuts if he sees the siphon or a net, even if its 30 feet across the room. He'll tolerate me during feeding, but as soon as he's swallowed the food, my hand had better not remain above HIS tank, or he'll come after it. Tank cleanings, needless to say, are always fun ;-)
Long story short, Cecropia, that's totally normal Jag behavior. I've found them to get more aggressive as they grow larger, so the tantrums will probably become more and more frequent.