Im a bit confused about the difference between serrasalmus gibbus and Spilo. On piranhaexotica.com they labeled a gibbus as a gold piranha. My gold looks just like that one in his photo. Are these the same fish? I also noticed that he labeled Serrasalmus Niger as "true black" piranha but I know that's wrong. Ive seen other sites that labeled pictures of gold piranhas as serrasalmus gibbus. So what da heck is a gibbus?