Pachypanchax

P. arnoulti has been in the aquarium hobby for many years but was identified as the congener P. omalonotus prior to its description. It appears in the majority of older aquarium literature under that name and as a result a degree of hybridisation has undoubtedly occurred.

For a number of decades this species was thought to occur throughout much of Madagsacar's western slope but populations immediately to the north and south of the range described above (see 'Distribution') are currently considered to represent unidentified species, while a number of populations from the Mahavavy du Sud and Betsiboka riv...

Type locality is given simply as 'Seychelles' and this species was originally endemic to the Granitic Seychelles, i.e., those islands in the centre of the group composed chiefly of granite rock. A translocated population now exists on Zanzibar while in the Seychelles it's known from the islands of Mahé, Praslin, Silhouette and La Digue.

The majority of original populations have already been extirpated due to introduction of invasive species such as Gambusia holbrooki and Poecilia reticulata, ongoing deforestation of the Ambohitra Massif, and physical diversion of the source of the Sakaramy River for domestic use by locals. An additional population may exist in a stream on the southern slope of the Ambohitra Massif on the road between Bobasokoa and Anivorano, near the village of Andranotohiliny, but this requires verification.