Unknown fish in fishbowl

Question
Hi

I have a fishbowl with 4 fishes. 3 of them are normal but 1 is not. it stays at the bottom, lays down with the glass and doesn't eat food too much. it's eyes glow at low light. But strange thing is that it only moves when nobody is around. It is thin and very flexible, it can swim super fast. When I turn the lights off, it starts dancing like a dolphin.It doesn't take oxygen too much as well. It wasn't causing problem until recently. It is chasing around all the other fishes. sometimes it wants to byte its neighbors.
I searched for the fish on the net but couldn't find anything about it. I don't even know its name. I uploaded a photo of it. please let me know what fish is it and what can i do with it?(It's not eating food and troubling others.)

http://img6.imageshack.us/img6/1045/unknownfish.jpg

Thanks in advance.

Answer
Hi Ayaz,
You have a big problem. the fish is an african ghost knife and i have one that looks cramped in a 1,000 gallon pond. he's 5 feet long.
Do every thing you can to get him out very quickly. give him back to the petstore unless you have a 500 gallon tank.

Also, a bowl is really too small for any fish. if i had to keep fish in a bowl, they would be feeder guppys.

What are the other fish in the bowl?
Good luck,
Wll