I won't encourage you to go into keeping just 3 pieces in there for firstly do you have planning of where and how big of a tank are you keping them. Secondly, even when they're small, they will start fighting in the tank unless you got enough to crowd them together. trust me for even you are keeping alot and they're just merely 5 inches, they're already killing each one another in the same tank. But I won't say it's impossible to just keep 3 of them in there, you never try you never know. Just got to be very observant and prepare to remove any injuried pieces in there.