As with most of the reptiles commonly kept as pets, malnutrition associated with poor hygiene and sanitation is the leading cause of illness among captive water turtles. Water turtles are, for the most part, carnivorous (meat eaters). Malnutrition results when these pets are fed primarily a vegetarian diet or inadequate sources of animal protein. Water turtles must feed within the water, and in so doing, the most important part of their artificial environment becomes easily fouled. This contamination is greatly exaggerated by the small amount of water usually provided for captive water turtles as compared with the almost unlimited aquatic habitat enjoyed by wild water turtles. As previously mentioned, captive water turtles should be fed in an environment separate from their living environment in an effort to control contamination. This is especially necessary in feeding water turtles that prey on live food and tear at it, creating particulate waste. However, species that gulp and swallow prey items whole (Snapping Turtle, Mata Mata) are usually allowed to feed in their artificial aquatic habitats because they are generally considered "clean feeders."
Commercial Diets are preferred for captive water turtles. These include Purina Trout Chow (Ralston Purina, Checkerboard Square, St. Louis, MO 63164), dry fish-flavored cat food, and balanced tropical fish food. These foods should first be offered to water turtles when they are very young so they become accustomed to such a diet. Commercial diets are substantially fortified with vitamins and minerals, are convenient and easy to feed, create minimal water contamination, and are bacteriologically clean. The last point is important because many water turtle diseases are contracted through contaminated food sources. Feeder guppies, goldfish and other live food (earthworms) may be diseased or may carry potentially harmful bacterial diseases of fish are often readily transmitted to other cold-blooded animals, such as water turtles.
Fish: If live or killed fish (guppies, bait minnows, goldfish) are offered to water turtles, they must be offered whole. Feeding just the flesh leads to vitamin and mineral deficiencies. The same problems result when captive water turtles are fed only small chunks of meat or hamburger, and no other items. A soft shell and swollen eyes are the usual signs of this particular dietary problem. Exclusive or excessive use of goldfish or frozen fish can result in thiamin (a vitamin) deficiency. Excessive use of fish high in unsaturated fish oil acids, such as mackerel, may result in a vitamin E imbalance and steatitis (inflamed body fat). Though adult water turtles are considered carnivorous (meat-eating), many juveniles are, in fact, omnivorous (vegetable-eating and meat-eating). Water turtles usually change from a mixed vegetable-meat diet to an all-meat diet after the first year of life. Consequently, about 25% of the diet of young water turtles should consist of vegetable matter (seaweed, spinach, broccoli tops and leaves, mustard greens, grated carrot and carrot tops, celery leaves). Addition of carrots (high in vitamin A) to the diet helps prevent 'swollen eye syndrome.' Pet Cal tablets (Beecham Labs, Bristol, TN 37620), a meat- flavored mineral (calcium and phosphorus primarily) and vitamin D3 supplement for dogs, are readily accepted by water turtles. Care must be taken to break these tablets into pieces that can be easily swallowed by the turtle. Pet-Tabs (Beecham Labs), which are vitamin-mineral supplement tablets for dogs and cats, can be similarly offered to water turtles. These supplements can be offered on feeding days or on alternate days. Some water turtle species, such as the Mata Mata, feed on live food or only specific prey items (Malaysian Snail Eater). These prey items should be as healthy as possible. With persistence and patience, many of these turtle species in captivity can be converted to commercial diets.
Feeding Schedule: Water turtles can be fed daily or 2-3 times weekly, depending upon their age and size. Rapidly growing juveniles should be offered high quality food daily, whereas adult water turtles do very well when fed 2-3 times weekly. Under no circumstances should water turtles be overfed. In the wild, the only opportunity for water turtles to overindulge is when they feed on the submerged carcass of a dead animal. Overfeeding captive water turtles causes them to become overweight and fouls the water.
‘I am generally impressed with the information this site provides for aquatic turtles. However, I am concerned about the contents of the section on turtle feeding. The site claims aquatic turtles are mostly carnivorous and that pet turtles should be fed accordingly. Scientific literature, field guides, and knowledgeable turtle keepers, however, show that the opposite is closer to the wild condition. While young aquatic turtles are indeed mainly carnivorous, as they mature plant matter becomes an increasingly larger part of their diet. This diet switch is a well-documented phenomenon across a number of species. Turtles in captivity, including snapping turtles, thrive with a balanced omnivore diet. Aquatic plants and leafy greens should always be available for turtles to nibble on. And as a staple, I think Reptomin or Mazuri are better than trout chow. These diets were designed for the specific needs of aquatic turtles.” - Ingrid Hitron