Three Stripe Pencilfish

About

The three stripe pencilfish (Nannostomus trifasciatus) is one of the more widely available members of its genus, found across a broad stretch of South American blackwater and clearwater habitats spanning the Peruvian, Bolivian, and Brazilian Amazon basin, the Rio Negro, and river systems in Guyana. Its most recognizable feature is the trio of dark horizontal stripes running along the body. A primary central band flanked by an upper and lower stripe. Worth knowing: if you flip on the lights after dark, you may not recognize the fish at first. Like most pencilfish, it switches to a vertically barred pattern at night, and this shift appears to be an automatic biological rhythm the fish cannot consciously override. Despite a reputation for being relatively easygoing by community standards, this species runs hotter than most of its relatives when it comes to intraspecific aggression. Males spar regularly, and in cramped conditions things can escalate beyond posturing. The solution is a spacious tank with plenty of visual breaks in the hardscape, and a good-sized group of ten or more individuals so aggression is distributed rather than focused. It occupies the middle and upper water column, making it a natural pairing with Apistogramma and other dwarf cichlids that hold lower territories. In the wild it feeds on small invertebrates, and in the aquarium it accepts a varied omnivore diet without much fuss.