Lovely specimen. Thank you for sharing.
Pier Aquatics is a famous place and I'd normally trust their ID. (Is the guy's name Neil?)
But this strikes me as the true piraiba in the body and head shape. The spots on capapretum at that size are significantly bigger and fewer than this fish displays.
We on MFK, as a community at large, have learned of the difference between filamentosum and capapretum and how to ID relatively recently, within the last 5 years.
I could be wrong still. I wish others chimed in to help you (which you may not need), Daz, and me.
GiantFishKeeper101
Rpul
vincentwugwg
H
HELIOX
fishtankphil
Tripletail