Puffer fish are so called as they have the ability to inflate their elastic stomachs with water or air. This is usually a response to some kind of threat, although in the aquarium many specimens appear to inflate themselves for no apparent reason. The fish becomes 2 or 3 times its normal size, big enough to scare away many potential predators, or difficult to swallow.

Puffers also have several other interesting adaptations. They are one of the few fish that can actually blink or close their …

Puffer fish are so called as they have the ability to inflate their elastic stomachs with water or air. This is usually a response to some kind of threat, although in the aquarium many specimens appear to inflate themselves for no apparent reason. The fish becomes 2 or 3 times it's normal size, big enough to scare away many potential predators, or difficult to swallow. Puffers are also one of the few fish that can actually blink or close their eyes.

Many parts of the body of puffers cont…

Formerly known as Eutropiellus buffei, this midwater swimming, diurnal catfish is very often sold as "Debauwi catfish". Pareutropius debauwi is a closely related species which is, in fact, seldom imported. Adults of the two species can be distinguished by several characteristics. In buffei there are three lateral stripes along the body, whilst debauwi possesses only one. Buffei also has black spots in the upper and lower parts of the caudal fin, and the fin itself has rounded lobes. Th…

Lungfish are among the most intriguing of "oddball" aquarium subjects, being able to survive in the most extreme conditions. They are very ancient fish, having remained virtually unchanged for millions of years. Some of the natural habitats of P. dolloi are wet for only part of the year, and it has developed several incredible adaptations in order to counteract this.

When the waters begin to recede, the fish will find a suitable nesting site, usually amongst heavy vegetation. Here …

The common name of this surface-dwelling species is derived from it's appearance when viewed from above, the large pectoral fins giving it the appearance of a butterfly. In reality, these fins serve a dual purpose. They help to camouflage the fish, making it look like a dead leaf floating on the surface, and along with the caudal fin, power the incredible jumps that it is capable of making. The fish jumps from the water to catch flying insects or to escape potential predators and it can mak…

Still widely referred to as hoplosternum thoracatum the hoplo cat is a popular and hardy fish. These fish have the ability to breathe atmospheric air by gulping down mouthfuls of air and the oxygen is then absorbed into the bloodstream through the intestine. This allows the fish to endure poor conditions in the wild but it can still be observed exhibiting this behaviour in captivity.

The hoplo is also eaten as a food fish in parts of South America….

Like the closely related Polycentrus species from South America, with which it is sometimes confused, this fish is camouflaged to mimic a dead leaf, both in body shape and pattern. It can also change colour to match its surroundings. When hunting, it stalks its prey in a head-down stance, appearing to drift towards it like a dead leaf drifting in a current. In reality the fish is propelled by tiny movements of its transparent hind fins.

When it strikes at an item of prey, the entire mouth pro…

Also known as Peter's elephantnose, this fascinating species is currently the most common Mormyrid in the hobby. Sadly, its popularity means it is often kept in unsuitable conditions. To deny the fish a soft substrate really is cruel, as it uses its "trunk" to locate food hidden in the substrate. It also needs dim lighting, and will commonly become withdrawn and pine away if kept under bright lights. If you cannot provide suitable lighting, add food to the tank at lights out to al…

This fish is usually imported as Pseudomystus stenomus but actually seems to be an undescribed species, as it's collected from the Malay Peninsula. P. stenomus is endemic to the island of Java and supposedly exhibits a higher degree of light-coloured patterning on the body.

The genus Pseudomystus contains many similarly-patterned species, of which the most common in the hobby is the Asian bumblebee catfish, P. siamensis. This can easily be distinguished from P. sp. cf stenomus by its cha…

This species was formerly included in the genus Leiocassis, and is still referred to as such in a great deal of the available literature. The current genus Pseudomystus contains many similarly patterned species, some of which may be being imported and sold as P. siamensis. Its commonly encountered congener is P. stenomus, but this can be plainly distinguished by its lack of "bumblebee" patterning.

The Asian bumblebee can also be easily told apart from the South American Pimelodid &q…