You can feed a red eared slider crickets which are easily found at your local pet store. Crickets are high in nutrients and have the natural appeal that will interest your turtle. You can also find different types of general turtle food at your local pet supplies store.
Good commercial turtle food, fresh veggies (lettuce, carrot, spinach, etc. - experiment!), anacharis, and snails (I grow snails for mine - great calcium source) keep Mr. Tuttle happy and growing.
You can feed your red eared slider fresh leafy green such as spinach and lettuce you can also feed them shredded carrots. My red eared slider (kevin) loves can shrimp that we buy from pets smart and live crickets
Feed your red eared slider food pellets from the vet and fish food is a healthy snack for you red eared slider and it eats fishes too.
My friend has 2 red eared sliders and besides turtle food pellets everytime she sees a spider she catches it and feeds it to her turtles
Bugs and fruits and turtle food