i got 12 in a 30 litre tank together and they are fine -- awaiting move into 240 litre tank -- they are known as "peaceful bettas" and they are very peaceful together
they hunt for food differently than normal bettas - they really hunt - very interesting to watch and very colourful
they need to have indian almond leaves in their tanks as the majority of them are wild caught and still need the tannins from the IDA's to keep them healthy
google the imbellis for more info hun but they are perfect for community tanks and species tanks
I got some of mine from [Mod Edit] (think thats the name on ebay) and some from my lfs special order