Just to clarify my reasoning some more. I've attached an image on my own fish, which I believe is
C. amazonarum. The four hard fin rays are obvious (arrows), and backed up by my direct observations of the fish. Note that the hard rays look more 'solid' where the meet the body than do the soft rays. Also note the scales running up between the dorsal rays. As far as I know this is a trait unique to
C. amazonarum.
Next, I've reposted the second photo of the OP. I agree that the image is not definitive in terms of the hard anal fin rays, but my interpretation is that there are four, and I don't think it amounts to just guessing. The first three rays are faint but obvious, and the fourth seems reasonable given that its appearance differs from the fin rays behind it, plus the attachment to the body looks more solid than the soft rays, as I described above. Again, the scales that extend up the dorsal fin are characteristic of
C. amazonarum, unless I'm misinterpreting the character completely.
If the fish has only 3 hard anal fin rays it cannot be
C. amazonarum, but then you would have to address the issue of the scales that extend up the dorsal fin. Of course, it's possible that this complex of acaras simply isn't documented well enough to make any definitive claim about species identity.

