The genus Fluviphylax can be found in a widespread area along the Amazone river, in east Colombia's and Venezuelan upper Orinoco region and from the larger rivers in the Guyana's. I personally was able to collect a member of this genus in Guyana, along the Essequibo river shores, opposite of the town Bartica.

The species dwells at the shores of big rivers but only in shallow shorelines covered by trees and/or dense vegetation. The species are small and fragile and form schools that swim along the edges of the waters.

Fluviphilax pygmaeus is the type species of this genus. Other known species are F. gouldingi, F. obscurus, F. palikur, F. pygmaeus, F. simplex, F. zonatus and F. wallacei.

Unfortunately the members of the genus are very fragile and collected fishes die often in transport if no oxigen is at hand. Therefore it is very hard to keep them alive during trips or while collecting more than one day in an area. Later on your trip it is hard to find the same type of water to make water changes. Therfore it is neccesary to take some extra water from the collectingspot in a seperate bag or container with you.

With the above knowledge collectors will have better chance to get them to their homes alive.

The name Fluviphylax represent the description for " Guard of the River". I assume this is because the genus is mostly present along the shores of blackwater rivers with sandy shores. On places they live, mosquitos and small other insects can be found at the watersurface. Fluviphylax predates mainly on these insects on the surface.

Literature:

Whitley, G.P. Some fish genera scrutinized. Proceedings of the Royal Society of New South Wales 65: 25.

Myers & Carvalho, in: Myers 1955 intruduced the genus name Potamophylax for this genus but it was a pe-occupied by an insect in the family Neuropteridae, Wallegren 1891.

Costa, W.J.E.M. 1996. Relationships, monophyly and three new species of the neotropical miniature poeciliid genus Fluviphylax (Cyprinodontiformes: Cyprinodontoidei). Ichthyol. Explor. Freshwat. 7(2):111-130.

Bragança, P.H.N. 2018. Fluviphylax gouldingi and F. wallacei, two new miniature killifishes from the middle and upper Rio Negro drainage, Brazilian Amazon (Teleostei, Cyprinodontiformes, Cyprinodontoidei). Spixiana, 41 (1): 135, figs. 1-2.