None bettas are fighter fish and will kill all the other fish.

The only chance you may have may be a plecostomus sucker fish used for cleaning the algae.

Here is a compatibility chart. It tells wich fish will get along with it.
http://www.oneworldinternetcafe.com/bet ... table.html

No fish can live with bettas. Betta fish are agressive and can kill another fish. If you really want a new fish you can get a divider. They separate fish. They may still jump over it. You could get another bowl too.

Fish that do not have bright colors and/or large fins should be fine with bettas.

With that being said you can probably get:
a pleco
short finned zebra danios best in a shoal of at least 3
Peppered or albino Cory Catfish best in a shoal of at least 3
Black skirted tetras best in a shoal of at least 3
Black neon tetras best in a shoal of at least 3

Thats about it. Just make sure there is enough room in the tank for additional fish and the betta should be fine.

Good Luck

There are tons of fish you can keep with a betta.

I kept my last one in a 15 gallon planted tank with cardinal tetras corydora catfish oto catfish and a couple of amano shrimp. My betta died though almost 6 years later.

Small schooling fish are best like tetras and rasboras. Bottom dwellers go well and sucker fish types though most sucker fish are terrible for small tanks.

While the betta does not kill other fish like the monkeys keep repeating they are territorial and for a betta community nothing less than a 10 gallon tank should be used. Schooling fish must be kept in schools 6 of one species not 6 of 6 species And having planted areas in the tank is of utmost importance.