There is the well known type, the pink tailed chaleus, "Chalceus macrolepidotus " which i have two of, the erythrurus is often refered to as the gold tailed hence why i think its a possibility, but discriptions vague,esp as fish shops name them what they want to sell them, Have you checked "Hydrocynus goliath" as you said with teeth, http://www.pbase.com/pschia/image/13855980