Macropodus opercularis

This, in the form found in pet stores, is not a natural fish, but will have been bred, probably line-bred, for many generations. It does occur in the wild, though, throughout southern China, Taiwan and northeastern Vietnam. According to IUCN, this is a common fish.

If you have information about or footage of this fish in the wild, please reach out to us.

Apparently, in the early days of our hobby, this this was everyone's favourite. It may have been the first non-native fish to have been kept in European aquarium. It is not hard to see why: the males look stunning; they are incredibly hardy; they don't need current of heating; they eat everything; they are easy to breed.

Nowadays, it takes an old-fashioned shop to carry them. Do keep them though, if you can. A heads-up: the males are aggressive and territorial, though hardly as much as suggested online, and they can reach 10-12 cm. Like their tropical counterpart, Betta splendens, they are not very active swimmers, so a 80 cm tank will suffice.

Keeping a pair together does not seem to cause problems, unless you count breeding as one. These are among the most prolific fish in the hobby, and you will easily have hundreds of fry on your hands. They are tiny and challenging to feed, which will be a blessing in disguise if you don't have a destination for the fry.

Paradise fish have a labyrinth organ, meaning they can extract oxygen from air and do not depend on oxygenated water to survive and can manage in sluggish circumstances. This means flow or surface agitation in your tank is not a necessity. Do however keep in mind that an aquarium filter has another important function as well: to keep ammonia, nitrite and nitrate at minimal levels. These are after all relatively large fish with a relatively large output.