Red-eared sliders are generally most active during the daytime, so they should be fed during this time. Many turtle owners stick to an every-other-day feeding schedule. Captive-bred turtles generally exist happily on commercial aquatic turtle foods. Some owners prefer to feed live foods or to supplement a packaged-food diet with some additional choices. Probably the most common live food offered is crickets. Crickets are fairly inexpensive, easy to keep without too much trouble, and an excellent meal choice for turtles. Other owners feed their turtles earthworms, mealworms, and raw fish.
In the wild, turtles are mainly herbivorous. In captivity, red-eared sliders will appreciate a few pieces of vegetable matter, in addition to their regular diet. These can include carrots, lettuce, cabbage, beets, cucumbers, and many other vegetable varieties.
How often you feed your turtle, what you feed him, and how much he gets at each feeding should depend, at least in part, on how old he is. In the wild, young turtle specimens will eat a variety of plants, insects, snails, and crayfish several times a day, while older turtles rarely eat anything other than soft, aquatic vegetation and tend to eat much less often. Observe your turtle carefully to make sure you feed him as much food as he requires to stay healthy but not enough to make him sick or overweight.