Very strange! I suggested Alestiidae just because it reminds a bit the Hydrocynus. But looks like soooo different from a photo of Hydrocynus goliath that I have (a taxidermy specimen, but very well prepared like other fishes in the same museum). This fish in the aquarium measures only about 30 cm lenght, have a much more hydrodynamic shape with no "small head and fat body", don't have longitudinal dark stripes, the background colour is silvery instead brownish, only the caudal fin have red instead dorsal, anal and caudal being orange, and the caudal fin lobes are very pointed and thread-like instead rounded.
I will investigate through alestiids and Hydrocynus. Maybe I can find something. Thanks!