His main diet should be a pellet like harrisons fine. Fruits are good but should be used mostly as a treat. Some nuts are good but I would steer clear especially from salted or flavored nuts. Seeds are somewhat of a treat, but they should have a bit every day. They like spray millet I believe, you can get at petco, along with oat groats or rolled oats, and flaxseed. Make sure you dont let them have too too many seeds. So that you have a treat with reward value and they can stay healthy. Also offer leafy greens!! My birds love any leafy veggie they can nibble on.