Are wild bettas okay? If so, I want to put in an entry for the 'warm' category.
This is Mr sp. apiapi (I don't name my fish), a member of potentially the smallest species of betta discovered thus far. He is just over an inch long from head to tail and is the best father in my fish room. He almost always has a nest full of eggs or fry to look after. He is also rather shy compared to some of my other fish.