Asian Mystic Catfish

Sisorid catfish like this one solve the fast-current problem with yet another design: a thoracic adhesive apparatus made of modified skin folds on the belly, distinct from the fin-based suction discs hillstream loaches use for the same job. Give it real current and enough dissolved oxygen and it'll graze biofilm nonstop; put it in still water and it struggles.

Care level: Easy · Temperament: Peaceful · Max size: ~5" · Min tank: 30 gal · Diet: Omnivore, algae + sinking wafers