I was reading about this the other day because we got a "rope fish" at work the other day and I was wondering the same thing... According to some stuff I read it is a type of polypterus. Erpetoichthys Calabaricus is the actual name of it but a lot of people call it a rope fish or a reed fish etc... But a lot of places seem to mislabel them as the Senegul Bichir or Polypterus sengulas. all around they are a cool type of poly that doesn't seem to get to big and is very peaceful