anostomus

Anostomus is a genus of freshwater fish belonging to the family Anostomidae, commonly known as anostomid or headstanders. These fish are native to South America, found in various river basins including the Amazon, Orinoco, and Essequibo. They are characterized by their distinctive upward-pointing mouth and their habit of swimming in a head-upward posture, especially when foraging.

There are several recognized species within the Anostomus genus, with Anostomus anostomus, the common anostomus or striped headstander, being one of the most well-known. These fish typically inhabit clear, flowing waters, often in areas with submerged vegetation or roots where they can find food. Their diet primarily consists of algae, plant matter, and small invertebrates.

Anostomus fish are generally peaceful and can be kept in community aquariums, though they are best suited for larger tanks due to their active nature and eventual size. They are diurnal, meaning they are most active during the day. In their natural environment, they are often seen in small groups, and their unique swimming style helps them to feed on surfaces that are not accessible to fish that swim horizontally. The genus name "Anostomus" itself is derived from Greek, meaning "mouth upward."