Hi,

from my experiences with raising bettas, I found out that bettas are
generally peaceful in a community tank. The only precaution is to
refrain from placing any anabantoids (labryinth fish) family. These
fishes includes paradise fish and gouramis. Since they are from the
same family, the betta will view them as a threat and will flare at
them, sometimes even ended up in fights.

cheers