Lol in my line of work I am familiar with seditives to calm ppl down u could just toss some of those in the tank it would chill right out. But i dont sugest it
I heard somewhere that alka selzer will do that. Anybody wanna try it out? LOL!
Seriously though, in the future, keep in mind that most fish can be subdued by placing them in the dark. Taping a piece of heavy paper around the tank would have chilled him right out.