Our old tank setup included a Beta with a bunch of other fish and he was fine.

( http://petoftheday.com/talk/showthre...highlight=fish )

The Siamese Algea eater left the beta alone and did a great job keeping the tank clean. They're kind of pretty too.

Our tank is a 15 gallon. They say to keep your fish to tank ratio at 1 gallon for each inch of fish you have. (Keeping in mind growth)