Looks like one of the many Machaca species to me. A Characin related to the Neon tetra, usually lumped into Brycon guatamalensis.I got quite a few Dovii that size and a couple bigger. They pull extremely hard and try their best to get back into the snags where they live.
That fish is called a Machaca.
I catch them as juvies in small tributary streams in Panama, and keep them in my 180 until they get too large for the tank.









