Axelrodia

The ruby tetra, Axelrodia riesei, is a tiny characid known only from the upper Río Meta basin in Colombia, part of the Orinoco system. It is less often seen in the hobby than A. stigmatias, presumably because of its remote, restricted range, and differs from it in its deeper body and red colour, which can fade after a period in aquaria. It is said to inhabit blackwater environments, and its small size and somewhat specialised requirements make it a poor community fish.

Axelrodia stigmatias is a tiny characid from the western Amazon region in Brazil and Peru, sometimes traded as the 'white star' or 'pepper' tetra. It resembles A. riesei but has a more elongate body and is silvery yellow in life where that species is red. It is said to inhabit blackwater environments, and given its small size and somewhat specialised requirements it is best kept alone or with diminutive, non-aggressive characids and small catfishes.