Evil Clown knife

[Richer]

Please don't take any offense, but I agree with aznufo, you should have done your research before you got a clown knife. Unfortunately thats how clown knife fish can be. They can grow up to lengths of up to 3 feet... and imo, a 120gallon is a bit too small for one clown knife. I would go with a 180gallon tank. Generally, they should be kept alone. They've been known to kill fish larger than they are (as you saw)... not to mention fish that are the same size or smaller.

There's nothing much you can do... either find someone who can take in your clown knife, or get it (or the other fish) another tank.

Sorry about your loss.

-Richer