You should try greens whenever you can, but my turtle ignores them too. Kale was the most successful but don't give them feeder fish because they can carry a lot of parasites. It's too risky and they get their protein from the pellets and sticks. If you want to offer live food you can give them crickets, or dried crickets. I just give mine freeze dried bloodworms and that works fine.
You can also offer cuttle bone which is a calcium source, just peel off the plastic on the top when you break it apart.