Metynnis lippincottianus is occasionally seen for sale, sometimes under the name of "Silver Dollar". It is easily distinguishable from m. argenteus and m. hypsauchen (which are more commonly sold as Silver Dollars) by its spotted pattern, hence the common name. M. lippincottianus shares a common name with m. maculatus but the two can be distinguished as the spots on m. maculatus are more pronounced.

Silver dollars are common and popular fish in the hobby. They are related to piranh…

Metynnis hypsauchen is sometimes referred to as the Plain Metynnis in an effort to distinguish it from its close relation, Metynnis argenteus. Both fish are sold in the hobby under the name "Silver Dollar" and are virtually indentical in terms of appearance and care requirements. The two species can be told apart as m. hypsauchen has a black blotch located slightly above and behind each eye. This species also occurs in a striped colour form which is sometimes referred to as(m. hypsauch…

Metynnis argenteus is very similar to another member of the genus, Metynnis hypsauchen and both fish are sold in the hobby under the name "Silver Dollar". The latter species is sometimes referred to as the Plain Metynnis in an effort to distinguish it from its close relation. They are virtually indentical in terms of appearance and care requirements. The two species can be told apart as m. hypsauchen has a black blotch located slightly above and behind each eye. In addition to these tw…

Known as the tambaqui in its native countries, this is the second largest species of scaled fish found in the Amazon basin. This alone should tell you much of what you need to know about its suitability as an aquarium inhabitant. In reality, it's debatable as to whether the species should be considered an aquarium subject at all. While pacu rarely reach their maximum size in captivity, they're still easily capable of growing to a couple of feet in length. The myth that fish will only g…

Know as the pirapitinga in its native countries, this is the one of the largest species of scaled fish found in the Amazon basin. This alone should tell you much of what you need to know about its suitability as an aquarium inhabitant. In reality it's debatable as to whether the species should be considered an aquarium subject at all. While pacu rarely reach their maximum size in captivity, they're still easily capable of growing to a couple of feet in length. The myth that fish will o…

This species is not actually a piranha in ichthyologic terms, being monotypic and therefore unique. It was so named due to its general resemblance to true piranha, and the fact that it is quite closely related to Pygocentrus species. Mento means "chin", referring to the protruding jaw of the fish.

This jaw structure, along with the adapted teeth, is used in its natural feeding behaviour. It has been observed to swim at great speed into a selected target, biting hard as it collides w…

The tyre track eel is also referred to as the white-spotted spiny eel.

A member of the spiny eel family, which range across tropical Asia and Africa, Mastacembelus armatus is one of the more common species available to the hobby, along with the peacock eel ((Macrognathus siamensis)and the fire eel (Mastacembelus erythrotaenia). These species are all from Asia but there are some members of the family from Africa that are occasionally seen for sale. These majority of these species are from the …

A member of the spiny eel family, which range across tropical Asia and Africa, Mastacembelus erythrotaenia is one of the more common species available to the hobby, along with the peacock eel (Macrognathus siamensis)and the tyre-track eel (Mastacembelus favus). These species are all from Asia but there are some members of the family from Africa that are occasionally seen for sale. These majority of these species are from the Afromastacembelus genus, with the most common representative being the…

The genus Exodon is currently monotypic, with this single species having uniquely designed teeth. These allow it to rip the scales from other species. It's an ideal choice for those wishing to keep a large shoal of a predatory species without possessing the massive amount of tank space needed for a shoal of piranha or similar. A tank full of these makes for a very colourful and active display….

There are currently six described species in the genus Thalassophryne, of which T. amazonica is the only freshwater representative. The others (T. nattereri, T. maculosa, T. megalops, T. montevidensis and T. punctata) are all estuarine animals distributed along the western Atlantic coastlines of Central and South America and inhabit brackish-to-marine waters. They are members of the family Batrachoididae or toadfishes, of which most are exclusively marine species. All batrachoidids are ambush pr…