It is rather confusing for us regulars too. There are some differences between different variants of
and their cousins. However, over the lifespan of the fish, they change quite a bit, so it's very hard to say "well, it's this one".
I think the "window" in the tail indicates a western (e.g. Colombia/Peru) origin of the fish rather than the eastern variants from Brazil. But that's as far as I will go. There are others on here that probably can pinpoint more precisely.
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Mats