Don't feed frozen food when you can get fresh. Don't rely solely on food from the produce section. Lawn grass is very good, and grazing should be encouraged. Over-seed with clover, rye grass or other grass to provide nutritious new shoots. Dried food, such as alfalfa hay, are important for a well-rounded diet.
Wild tortoises rely on dried vegetation for food when the spring flowers and grasses are gone.
It is not easy to get them to eat dried foods in captivity. Powdered Iguana Chow or rabbit pellets, dusted on their food, helps complete their diet. The more time hatchlings can spend outside, with warmth and protection from hazards, the better. Even if they just sleep in the shade, bring them outside as much as possible when the weather is warm and dry. Quarantine any new tortoise.