HI

Welcome to FishLore.
I'm not certain what's going on with his lip (maybe a deformity from living in cramped quarters), but if he's not eating that may be a sign of distress or illness, which could potentially harm your other fish. Keep a very close eye on your oscars if you are not able to quarantine the big guy.
I just read that the Red Belly Pacu grow upwards of 42" and need a minimum 1200 gallons.
Unfortunately, many pet stores and chain stores sell these fish as aquarium fish... I suppose your
LFS has a policy against this, but I don't know why they had it in the first place. Perhaps your zoo has an aquarium that would fit him?
Poor fishy. I'm glad you were there to save him and I hope you're able to find him a suitable home.
