Giving nuts to your chao helps them become immune to illnesses and grow up. Different nuts will effect different skills. Common nuts effect stamina whilst GBA nuts, chao fruits and DC only fruits will increase skills and decrease some. To feed your chao, simply pick up a fruit and walk over to your chao and touch it and it will pick up the fruit and nibble it or may even wolf it down. For more information, see the Tree Nuts page.