Yes some more pictures to compare both types/species would be great.I had this same theory until I was able to see literally 1,000s of these fish right out of the wild.[...]I'll try to find some better pics that illustrate the pattern differences.
This would be interesting. All specimen I have seen up to now with this coloration and this typical shape always were youngsters.I'll look for some more pics, but they do not get much bigger. They are very gracile and the body size, even of an adult, is not much more robust than that of a Farlowella.
I have no doubts that this is a Sturisomatichthys species.I had forgotten this fish but found the pic in my collection. It was captured in the northern Magdalena.
best regards
Norman