Xenomystus nigri

The African knifefish is distinguishable from N. chitala by the absence of a dorsal fin, but resembles it in being a twilight species. Occasionally it emits a groan-like sound from the pneumatic duct, which links the swim bladder to the digestive tube. Size: 10-20 cm

• Pimelodus pictus
• Hyphessobrycon herbertaxelrodi
• Dermogenys pusillus
• Protomelas similis
• Metynnis argenteus (Serrasalmidae)