http://elmlaneaquatics.com/fish/tropical/

Siamese Fighting fish (Betta splendens)

As their common name suggests, these really rather odd little critters originate from Thailand, but also inhabit Laos, Cambodia and Vietnam, and have also spread more widely in the wild since becoming popular as pets and bred in captivity (escaped or dumped commercially bred ones have formed wild colonies in many places where the conditions are right for them, right across the globe).  Their natural habitat is the slow-moving (or not moving at all) swampland and paddy-field of the far East, where water levels vary widely across the seasons, so that from time to time they find themselves living in little more than a puddle, and at others they have a huge lake to swim about in. Sadly, many unscrupulous dealers have used the former conditions to justify them being sold in tiny plastic cups and jars, when of course to live healthily they need much more space, though their resilience to less than perfect living conditions has undoubtedly contributed to their massive growth in popularity.

Unlike any other popular small fish, betta fish need to be kept alone. They are not community fish, even with each other; in fact, males will literally tear each other to bits if kept in the same tank, and females will also attack males.  You can, with care, keep females together in groups of five or more (known as a ‘sorority’) but never mix the sexes.  Breeding is done under strict control, as after spawning, the male and female will attack and kill each other – in the wild, they have the opportunity to get away from each other once they have produced young: in a tank, that isn’t possible.  Opinions vary about possible tank-mates for betta fish: the safest option is to keep them alone in their own little individual tanks, though they can potentially share accommodation with small, peaceful bottom-dwellers like the smaller corydoras or loaches.   Don’t be misled by seeing them in some pet shops housed with other fish, such as guppies: this is only a temporary situation while they are young: to keep them in the same conditions is a recipe for disaster.  And bettas are by no means always the perpetrators of tank violence: nippy smaller fish will enjoy snipping away at their fabulous fins, given the chance, too.

On the bright side:  searching for a use for that way-too-small tank you bought when you first considered fish-keeping?  A perfect home for a solitary male betta.  They shouldn’t be kept in bowls, any more than any other fish, but can happily live in 30 litres or so.  Provide them with plants and hiding places to keep them occupied, especially close to water level as they are labyrinth fish (ones that nip to the surface periodically to breathe in air).  Some owners buy or construct ‘hammock’ type structures for their betta to rest in for this purpose.  They are hardy and cheap to keep: they may appear to be fussy eaters, but in reality just don’t really eat very much: they should take good quality flake or small pellet food, and particularly enjoy bloodworm, but be careful not to overfeed.  And they are usually spectacularly beautiful, even the rather less showy females.