Upside-down catfish

[1] However, a number of other fish may also be known by this name: The name 'dwarf upside-down catfish' is also used for small (around 10 cm) species of the catfish genus Synodontis.

In the aquarium trade, the name is almost always applied to S. nigriventris or species with which it may be confused, such as S. aterrima, S. contracta, and juvenile S. nigrita (adults of which are around 20 cm so are not "dwarf" species at all).

One theory accounts for this unusual behavior as a feeding strategy.

In the wild, it often grazes on the undersides of submerged branches and logs, and swimming upside-down makes these areas more accessible.

[7] A different theory suggests swimming upside-down makes aquatic surface respiration more efficient.

Synodontis nigriventris , shown here, is commonly confused with species such as Synodontis aterrimus , Synodontis contractus , and Synodontis nigrita , all of which may be sold to aquarists as the "upside-down catfish".