Juruena

Boulengerella maculata is a pelagic ctenoluciid found throughout much of the Amazon, Orinoco and Tocantins river systems. Colour pattern varies considerably, with some specimens much paler than others, and this may be correlated with water type. Random dark spots on the upper body, and a dark stripe only behind the eye when one is present, separate it from the similar B. lateristriga. It reaches 329 mm SL and needs an aquarium with base dimensions of 240 by 90 cm or more.

The black stripe tetra, Hyphessobrycon melanostichos, is a characid endemic to the Rio Doze de Outubro in the upper Rio Tapajos basin, Brazil. It shares a number of similarities with Hyphessobrycon sp. 'Blue Ribbon' but has a lighter, more streamlined body, a smaller humeral spot and red colouring. It can become territorial in small tanks, but a group of 10 or more should prevent problems.

Hyphessobrycon vilmae is a small characid that appears to be endemic to the upper rio Tapajós basin in Amazonas and Mato Grosso states, Brazil. It is occasionally traded as 'chocolate neon tetra', and has a continuous, solid dark lateral stripe with no obvious humeral blotch. Generally peaceful, it is best kept in a mixed-sex group of at least 8-10.

The serpae tetra, Megalamphodus eques, is a characid with an enormous range through much of the Amazon drainage and the Río Paraguay. Very common in the trade, it is also sold as the 'jewel', 'red minor', 'blood' or 'callistus' tetra, and ornamental strains include 'long-finned' and 'balloon' forms. It has a reputation for nipping the fins of tankmates, although this is most pronounced when too few are kept or space is limited.

Boulengerella cuvieri is a pelagic ctenoluciid characin from much of the Amazon basin, the Río Orinoco and coastal drainages of the Guianas. The largest officially recorded specimen measured 675 mm, but it appears to grow larger, possibly beyond 800 mm. Given that size and its natural behaviour it is largely unsuitable for the home aquarium. Its entire dorsal-fin base lies ahead of the anal-fin origin, a character shared only with B. lucius and B. xyrekes among ctenoluciids.