The menu for your red eared slider
Red eared sliders need a diet that is a mixture of both animal and plant materials. Young red eared sliders eat more animal protein so babies are started off on a diet that is more on thecarnivorous side. It is still a good idea to offer vegetation to young turtles although they may not really start eating it until they get older (offering it early on at least makes it less likely they will shy away from trying it as they age). Vegetation should make up a significant part of the diet for adult red eared sliders.
Commercial pellets are fairly nutritious, are certainly convenient, and are beneficial since they contain a good mix of vitamins and minerals. However, as the saying goes, "variety is the spice of life." Offering a wide variety of foods is better than solely feeding a commercial turtle pellet as a variety of fresh food offers a wider range of nutrients in different forms (which may even be absorbed better when fed in the natural state).
Feeding a variety of items is also more stimulating to the turtle and a good form of enrichment. Live prey items are especially enriching, as they give turtles an opportunity to exercise by hunting as they would in the wild. Generally, try limiting pellets to about 25% of the diet, making up the rest with items from the following list:
Prey items: earthworms, crickets, wax worms, silkworms, aquatic snails, blood worms, daphnia, shrimp, krill, and meal worms. For very small turtles, prey may have to be cut into smaller pieces. Larger turtles can be offered larger items like tadpoles or feeder fish, though some experts warn that feeder fish may be carrying parasites, etc. and some fish (like goldfish) are too fatty to be fed regularly.
Leafy greens: collard greens, mustard greens, dandelion greens, kale, and bok choy. Head (iceberg) lettuce should never be fed as it contains very little nutrition but dark green leaf lettuces (e.g romaine) can be fed sparingly. Make sure you feed items with appropriate calcium to phosphorous levels.
Aquatic plants: In an aquarium or pond you can add aquatic plants on which turtles usually love to snack. Submerged plants like anacharis are often eaten as are water hyacinth, water lettuce, duckweed, azolla (fairy moss), and frog-bit.
Other vegetables: Carrots (tops are fine too), squash and green beans.
Nutritional Supplements for Red Eared Sliders
A good reptile multivitamin with calcium and vitamin D3 should be mixed with the food a couple of times a week. Also, an excellent way to provide additional calcium is by putting a cuttlebone in theturtle tank. These are often available in the bird section of your local pet store and can be affixed to the tank with suction cup clips or just floated in the water.
Tips on Feeding Red Eared Sliders
Catching wild prey items can be dangerous if they have pesticides on them. They can also give your red eared slider intestinal parasites. The same goes for vegetation, like dandelion greens, that you pick from the outdoors.
Vegetables can be shredded to make them easier to eat. This is especially helpful with smaller turtles.
Some experts recommend feeding fresh fruits such as bananas, berries, apples, and melon. However, this isn't really a natural staple in the red eared sliders diet and it may cause diarrhea. If used, fruit should be only in very small quantities.
Don't feed frozen fish, or at least not very often, as freezing some types of fish increases levels of an enzyme in the fish that destroys vitamin B1.
Cooked chicken and cooked lean beef don't offer balanced nutrition and these will foul the water very quickly. Use only as very occasional treats and feed only if you use a feeding tank outside of the main tank. The protein contents can also contribute to kidney disease in your turtle.
Never feed raw chicken or meat due to the risk of bacterial contamination to both you and your captive turtle who isn't used to being exposed to such things since he lives in a controlled environment.