I'm a sucker for B. Macrostoma. I was thinking I could get a 20 gallon. Plant it very heavily, and almond leaves, and then two pairs of Macrostoma (2 males, 2 females) to it.
I'll also hava an extra tank to place the males in if they spawn.
bettas that get along - now that's cool! Sounds like they're meant for big tanks only though... and I wonder how they'd react with other types of bettas...