In general, bettas will behave fine around fish that don't have big, bright fins and tails. Basically, if your current fish look nothing like another male betta, your betta won't have a problem with them. So just introduce it as normal, and then keep a close eye on it for a week or so to make sure there's no agressive behavior.
EDIT: Although, true, different fish have different reactions.
Last edited by bubblenest; 02-19-2009 at 05:44 PM.