Inpaichthys

The purple emperor tetra, Inpaichthys kerri, is a small characin from the Rio Aripuanã and upper Rio Madeira basins in Brazil. Also sold as the 'blue emperor', 'regal' or 'royal' tetra, it is sometimes confused with the emperor tetra, Nematobrycon palmeri, but can be told apart by its adipose fin (absent in Nematobrycon). It lives in sluggish, tannin-stained forest tributaries and has been spawned regularly in the hobby.