Its new home is so much better than the 10 gallon!
You can feed it earth worms and dark leafy greens. Feeder guppies are OK but don't get the walmart or petco kind. They have too many diseases that can really hurt the turtle. It would be good to gut load the guppies before feeding it to the turtle. Don't feed it iceburg lettuce. Limit the turtle pellets its getting. They're not good enough for a diet staple. If you can put that enclosure out in the sun do it, but make sure its not long periods of direct exposure. It needs UVB light to stay healthy and digest its food.
Here are a couple good turtle forums
- lots of good info
- not as active as the tortoise forum is