aussieJJDude said:I'd reccomend a large school - like 20 - of one of the boraras species. The great thing is that ib the wild the range of the betta and some bororas species tend tI overlap.
For me personally, I think the whole 'betta will kill other fish' is highly overrated. Having kept multiple males, they rarely get more aggressive than a chase - a few of my males were territorial and wouldn't allow other fish in his territory (around 8 inch in diameter - but would patrol the rest of the tank without trouble.
Good fish to mix would also be kuhlies - biotopically correct... - and cories as well. Fish that stay in the lower levels are usually fine - tetras, cories, loaches, rasboras - and they usually ignore them as well. Best bet is to stay away from surface dwelling fish - guppies, hatchets and gouramies - and some bettas are prone to having problems with fish with large finnage - like guppies - or brightly coloured - some tetras, or guppies.... but from my experiences, it is not the case.
I think my 'success' could also be due to introducing the betta after all my other fish, so the tank mates were already established and not coming into 'his territory' - aka the tank.