Pencilfish

About

The pencilfish (Nannostomus grandis) is the biggest member of its genus, though you'd be forgiven for not recognizing it at first. It looks deceptively similar to the much more common Beckford's pencilfish. The key visual tell is the absence of pale white or bluish tips on the ventral fins, plus a very well-defined central lateral stripe running the length of the body with no secondary or tertiary stripes alongside it. The upper body runs brownish, fading to yellowish on the lower half. It originates from the Belém region of Pará, Brazil, and shows up in the hobby mainly as bycatch in shipments of other Nannostomus species, so finding it intentionally takes some effort. Like its relatives, it performs a neat trick at night, switching from its daytime horizontal stripe pattern to a cryptic vertical barring. This shift is automatic and happens even in blind individuals, so it's hardwired rather than learned. In the aquarium it's a peaceful, middle-to-upper-column species that pairs well with dwarf cichlids like Apistogramma as a dither fish, and it rarely bothers fry. Keep it in groups of ten or more to encourage bold, natural behavior and distribute any mild squabbling. A forgiving choice for newer keepers who can track it down.