They don't need swimming space as such, but they will dart around the tank quite a bit, if they are happy. I am basing the recommendation on my housemate's tanks from a few years ago.
Compatible tank mates would be tetras, rasboras, peaceful dwarf cichlids, gouramis, and other peaceful community fish. I'd probably go for an Asian themed tank, if I was to keep them: 10-15 khulis, 15-20 rasboras of one species and 1m 3-5f honey gouramis.