Whether you keep a painted turtle (Chrysemys picta), slider (Trachemys scripta), softshell (Apalone spp.) or stinkpot (Sternotherus odoratus), you should provide the bulk of your pet's diet in the form of natural foods. However, in a pinch, you may be able to find a snack in your pantry that will tempt your terrapin. While none of these foods are likely to kill your turtle in small amounts, repeated use will likely lead to nutritional problems.
Canned Pet Foods
Most turtles will readily consume canned dog or cat food, but such foods are unthinkably messy, and guaranteed to turn the water cloudy. Try to reduce this occurrence by providing only a small amount of food at a time. Canned foods consisting of cut – rather than chopped or pureed – lean meats are preferred. Your turtles are unlikely to turn their nose up at any particular flavor, but fish- or poultry-based foods are probably the best choice.
Dry Pet Foods
Dry, kibble-type dog or cat foods are acceptable on an occasional basis. As much as possible, offer your turtle high quality, meat-based dry foods rather than those made mostly of wheat, corn or rice. You may have to break large kibble into smaller pieces – try to feed your turtle pieces that are smaller than the distance between his eyes.
Canned whole fish, such as sardines or anchovies, are acceptable for your turtle, as long as they are packed in water rather than oil and do not have any added salt. It is wise to rinse them in cool water before adding them to your turtle's tank. Canned shellfish, such as mussels or shrimp, are also good emergency foods if they are also packed in water and do not have added salt.
Canned Fruits or Vegetables
Most common canned fruits and vegetables, such as squash, green beans, peas, apples, pears or carrots, are safe to feed your turtle. As with canned fish, avoid products with added oil or salt and rinse them before offering. Acidic fruits and vegetables, including hot peppers (green bell peppers are safe) or citrus fruits, as well as pickled fruits or vegetables are not appropriate for turtles.
Fruit kept in your pantry -- fresh bananas, pears or apples -- are not only acceptable for emergency meals; they are suitable components of your turtle's maintenance diet. Be sure to peel bananas or other fruits with thick skins, but apples or pears can be sliced with the skin intact. Always wash fresh fruit before giving it to your pet.
Foods to Avoid
Onions, garlic and shallots are not suitable for turtles. Also avoid offering your turtle processed foods, such as crackers, chocolates, chips or breads. In general, it is best to err on the side of caution. Your turtle will not starve from missing a meal or two, but inappropriate food items may cause illness or death.