Is it true that if you have lots of turtles in the same tank big will kill smaller ones?

It is true that larger turtles can kill and eat smaller turtles if kept in the same tank. Turtles are territorial and predatory by nature, and they may see smaller turtles as food or competition for resources. The size difference between the turtles is a significant factor in determining the likelihood of aggression. A large turtle can easily overpower and consume a smaller turtle, even if the smaller turtle is of the same species.