Although memory can be a factor on some PCs, it's not usually the cause of the behavior that you describe. Fish Tycoon is designed to give priority to pretty much any other application that's running, whether it's in foreground or background mode - even system processes. So the 'stumbling and pausing' that you sometimes see is not a bug in the program, but a result of Fish Tycoon yielding priority to another application or process. It was an implementation decision that was made in order to keep Fish Tycoon from affecting system and other application performance, and to allow people to run FT as more or less a 'background' application (since its real-time design doesn't require constant attention to make progress in the game).