You want to offer very little fruit as it is no where near as good for them as veggies (fruit is high in sugars, veggies are not) and cockatiels are not well known for being fruit eaters.
Foraging is an activity where the bird has to search and work to get at its food- some of us have special toys that make the birds work harder to get their food and some of us just serve or hide food in ways that means the bird has to work at ripping paper or moving beads to get at what it wants to eat- this keeps them busy, interested, engaged, happy and stops them from getting bored and over eating. Foraging activities are fun for most birds and will reduce the likelihood of issues with boredom like screaming, plucking or other undesirable behaviours.
Cockatiels are well known to love fresh grasses and seeded grasses, broccoli and kale so maybe you can try some of those.
With birds we often find that they may ignore or reject a food for a long time before they accept that it may be edible or at least not likely to kill them lol. We keep serving things that they do not eat the first time (if it is good for them) until it is no longer foreign to them and we just keep our fingers crossed that one day they will take a little taste. I find my bird gets annoyed at things on the roof of his cage that do not belong there but only if they are above his night time perch so I can put a raw whole carrot there and he will destroy the whole thing and make tiny bits of carrot but if I put it in his bowl he won't touch it unless it is to through it on the floor- serve veg any and every different and creative way you can think of.
If you serve your chooks sprouts or mocrogreens then that is a wonderful food to offer your parrot too- ideally you want your parrot eating fresh veggies and grains daily as opposed to a as a treat so if he enjoys microgreens (sprouts are a bit better but microgreens are good too) then feel free to offer them daily.
and Welcome!
