Barred Pencilfish

About

The barred pencilfish (Nannostomus espei) stands apart from every other member of its genus in one immediately obvious way: those bold, vertical dark bars on its flanks are permanent. Every other pencilfish displays a similar barred pattern only at night as a resting coloration, then reverts to horizontal striping by day. This species keeps the bars around the clock, making identification easy and giving it a distinctly different look from its relatives. It comes from the Mazaruni River system in Guyana, where soft, acidic blackwater conditions shape its preferences in the aquarium. At barely an inch and a half when fully grown, it is a genuinely tiny fish, and that small size defines how you keep it. Despite being peaceful, it can get lost or outcompeted in a busy community tank, so it does best in a species setup or alongside similarly small, non-pushy fish. Dwarf cichlid keepers have found it makes an excellent dither fish for Apistogramma because it cruises the upper and middle water layers without bothering fry. Keep a group of ten or more if you can. Rival males will spar and fin-nipping within the group is normal, but spreading the social dynamics across more individuals keeps any one fish from bearing the brunt of it. Breeding is possible but genuinely tricky, so this one sits comfortably in the intermediate care bracket.