Hi neighbor! What have you been trying?
Most of mine like romaine lettuce, but they might eat them one day, and not the next. I have tried things like collards and mustard greens since those are supposed to have more vitamins and calcium than romaine, but I've gotten a less enthusiastic response with those.
I tried something new this year with pretty good results, dandilions! I had often read that dandilion greens were very nutritious, but I'd see those in the yard and for some reason I couldn't imagine them eating dandilion leaves after they had rejected collards, etc. They didn't look as crisp as romaine.
But this year I pulled some pretty big dandilion leaves, rinsed them off so maybe they would look a little more appealing and put them in the pen, and I had several go for it. I've had pretty good luck with that, but sometimes my timing is off and the leaves wilt before they are eaten. So, another thing I do when I have time is transplant some dandilions into their pen.
That way they stay fresh until someone decides to eat them.
I have a garden where I have been letting dandilion's grow, even though they don't look great, because they get pretty big the longer you let them grow, and I want to have a supply for the turtles. I transplanted a pretty big plant into the pen last night, and when I checked today, the plant had been devoured. Anyway, I would try different things.
Have you tried superworms with this turtle? You can usually get them at petsmart and one way I get greens into finicky eaters is to feed romaine to the superworms, then I feed the superworms to the turtles. You can also "gutload" mealworms and crickets this way.
Hope this helps?
PS-Have you tried tomatoes yet?