Rivulus foliiscola, n. spec. is described from specimens collected at a single locality at the outermost southern tip of the department Guainía, Colombia, where the Rio Negro flows into Brazil, and Brazil's borders, Venezuela and Colombia meet. This locality was only about 2 km distant from one at which two other undescribed species were collected sympatrically in a shallow forest creek. Rivulus foliiscola n. spec. lives in deep pits with standing water, a habitat type supposedly more suitable for annual fishes. The new species displayed unusual behaviors, e.g., it apparently preferred to live near, and spawn upon, the substrate. Rivulus foliiscola is also divergent in coloration and fin shape from other Rivulus species and evinces a characteristic "snake-like" behavior upon capture as if seeking cover. Initially, these traits lead the authors to suspect they had collected a new annual species. However, its lifespan in captivity for more than two years, the relatively short incubation period of its embryos, and the absence of embryonic diapause strongly suggest that it is a non-annual, and thus more appropriately referred to the genus Rivulus, family Rivulidae.*

Keeping and breeding is not easy.

Rivulus foliiscola lives in isolated sinkholes with no visible connection to any creek or running water. This non-typical niche appears more suitable for the annual rivulid species. With a thick layer of leaves at the bottom and surrounded by steep walls several meters in height, these sinkholes had only a small residue of rainwater at their deepest part, from which the fish were collected. It is possible but not confirmed that these sinkholes hold minimal water volumes even during the rainy season. No other fishes were present. The sinkholes may have resulted from the infiltration of groundwater. The forest border was near a seepage grassland, located about 3-4 meters below the forest floor, suggesting an abundance of water at that level that may well be present under the forest floor as well. No Rivulus foliiscola or other fish species was present in that seepage area, and the new species was not found elsewhere. Rivulus foliiscola n. spec., feeds mainly on terrestrial, aquatic- and flying insects, and occasionally also on small tadpoles that frogs deposit in their shelters.
Rivulus foliiscola hides in the leaf litter upon disturbance and remains in the curled leaves until forced out. Since the discovery of the new species in March 2018, wild specimens are still alive in captivity at the time of writing in  October 2020.

This suggests that their lifespan can exceed two years and five months, at least in captivity. It also means the species is not adapted to an annual lifestyle despite the ephemeral appearance of their habitat and their superficial resemblance to some annual species. Rivulus foliiscola is a "confirmed non-annual," as discussed by Thomerson & Taphorn, (1992).

Additionally, eggs were never deposited in mops or other floating material but only deposited on the substrate in a layer of leaves and coco peat.

Their lifespan can be up to 3 years in captivity.

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