I would say that's a pygo, with red eye it appears to be P. Nattereri.
The anal fin is also red which is very common in all the pygos, I have never seen a serra with that much red at anal fin, at least not at the size. without a good size shot it can be a bit tricky but I would think it's a Pygo.
If it were a serra indeed, then I would say maybe it's a sanchezi just because of all the color on it.