What Should I Do With My Krib?

[Carp4U]

My male krib is now in a tiny tank floating in my main tank. Everything was fine until i bought 6 cardinal tetras. He chased them and attacked them. I got him out and put him into the separate tank to allow the cardinals to settle in. I let him out and he started doing it again but very badly, they were all separated and stressed and couldn't escape from him. So i got him in again. I decided to let him out after a week or so. I came back from school one day to find only 2 alive. One was floating eaten in half, and 3 were missing. He had eaten them. He is fine with all the other fish, harlequin rasboras, cory, algae eater and plec.
So i put him in. Thankfully the other two who were alive are okay, and have settled in well, the krib however has been in the tank for well over 2 weeks now. He seems okay but want to take action soon.

My tank size is 15gal.

Should i take him back to the shop then buy more cardinal tetras?
Should i let him go and possibly kill my remaining, healthy cardinals and possibly attack and new fish that i bring into the tank? i want more!
Is there any other way?

I don;t have any other tanks for him.

Thanks

 

[kribensis12]

Cardinal tetra's are going to be attacked and eaten. They are too small.