I had a red belly piranha named killer.
A guy I knew in college bought a dozen piranhas, they were about the size of a fingernail when he bought them. When the grew larger, drunk people would put shit in the tank during parties like peanuts and pretzels, and random crap.
All of the piranhas died except one.
The following year, I started living at a house that had a massive fish tank that must have been 12-15 feet long. My friend gave me killer and he lived in a much bigger thank for a year or two.
It was killer, and a very large Pacu that was probably 12-16" long in the tank for a while. One of my roommates caught a good sized large mouth bass in the Mississippi river and released it in the tank.
I probably released like 36 feeder fish in the tank before I was going out of town for 2 weeks, and I was hoping the feeder fish would hold everyone over. When I came back, the largemouth bass had been cleaned to the bone.
I left the fish in the tank for the next kids that were going to rent the place. IDK what happened to them.