Lower left = red-tailed catfish Phractocephalus hemioliopterus
Smaller & striped = banded leporinus Leporinus fasciatus
Smaller & red fins = flagtail prochilodus Semaprochilodus insignis
The 3 big black b***ers = ripsaw catfish Oxydoras niger
You should be able to identify the freshwater stingray on the right hand edge quite easily too.