What fish can I keep with my male Betta fish in a 5 gallen heated tank?

[soho601]

I have a beautiful male betta fish in a heated 5 gallen tank, who I love. My boyfriend wanted to put more fish in the tank, so after much research we went out and bought a Pictus catfish, a bala shark and a silver tipped shark to add. (fish were all the same size as my Betta - around 1 inch long each)

We read that Betta fish would anly attack fish which looked like Bettas, with bright colors and flowing fins, so we thought these guys would get in fine together.

But my Betta went nuts when we introduced the other fish, chasing the (much bigger) fish round and round the tank and nipping at their fins. After half an hour we removed him and put him in his own tank as the other fish were getting stressed and he looked exhausted.

Now we don't know what to do. Should we persevere and leave them for longer to see if they settle down, or should we get a different species of fish? If so, can anyone reccomend a breed or breeds of fish which will get on better with a Betta?

(PS - we are aware that all the new fish we bought get very big! We have a heated 250 gallen tank ready for them next door if we decide to keep them until maturity.)