Fish That Start With U
Browse all aquarium fish species with common names beginning with "U". Each profile includes care requirements, water parameters, tank size recommendations, and compatibility information for freshwater, marine, and brackish species.
Welcome to the species index for the letter 'U', where you'll discover a fascinating variety of fish including both popular community dwellers and unique rarities. While we don't have any species starting with 'U' in our database right now, notable examples include the Upside-Down Catfish (Synodontis nigriventris) and the Unicorn Tang (Naso unicornis). This section highlights the diversity of the aquatic realm, showcasing both striking additions to your aquarium and historical species.
Uaru (Triangle cichlid)
Uaru amphiacanthoides
Uaru are big, mellow Amazon cichlids with that neat disc-and-triangle body shape and a surprisingly "gentle giant" vibe. They graze and pick at food all day, act super social when kept in a group, and they are famous for serious parent duty when they breed (both parents guard and tend the young).
Ubirajara rivulus (killifish)
Melanorivulus ubirajarai
This is a tiny Cerrado rivulus from central Brazil - the males show off neat red chevron-like markings, and they are always cruising the top and edges looking for snacks. Like a lot of Melanorivulus, it is a jumpy little personality fish that does best in a tight-lidded, plant-heavy setup with gentle flow.
Upside-down Catfish
Synodontis nigriventris
The upside-down catfish is a small African mochokid catfish famous for swimming and feeding belly-up, especially under cover and along the water's surface. It has a light belly (often with darker spotting), a darker back, and prominent barbels, and it is most active at dusk and night. Peaceful overall, it does best in groups with plenty of hiding places like driftwood and caves.
Urosema dwarf pike cichlid
Wallaciia urosema (S. O. Kullander, 1990)
Rheophilic (current-loving) dwarf pike cichlid from Brazil’s Tapajós system; a small, territorial predator (to ~6.8 cm SL) that benefits from strong filtration/oxygenation, broken sightlines, and plenty of bottom cover (wood/rocks/caves).