HI!
I would agree with Mallemalle...
The body shape looks similar to the
Pseudancistrus sp L67 from the RIo Xingu...
here are a few pic to compare:
L17 (which actually should be L67..!!;-)
LDA32 coming from the Rio Tapajos, the seam in the fins is not so yellow, a bit more orange ...
Cheers
Yann