I know this post is very old but for some odd reason people are still sold the Red-bellied Pacu as a friendly, vegetarian fish, nothing could be further from the truth! The school of 4 I have will eat nothing short of worms and other fish, I have tried tons of different fruits/veggies and it doesn't interest them at all, I have however finally got them to take pellets but only carnivore ones. l (3 weeks ago) added 2 red finned Piranhas into the tank, they have become a school now, they all move the same too. Funny thing is The Pacu lead the attack on other fish and the Piranha follow.