Yes, turtles can eat apples. But do not make it part of their daily diet.

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You can feed an apple to your pet turtle on rare occasions as a treat only.
Before feeding an apple to your turtle, you must wash and clean it thoroughly.
There should not be any remains of pesticides on the apple.
You must remove the peels and seeds from the apple before feeding it to turtles.
Seeds contain some content of poison, which can make the turtle severely ill.
How Much Apple can a Turtle can Eat?
Turtle is an aquatic animal and cannot produce enzymes that are essential for digesting apples.

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Break down of sugar and acid is possible through such proteins.
But due to the lack of digestive enzymes, the digestion of apples takes a long time.

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It creates a bloated stomach, which causes severe pain in the stomach.
Warehousing people use many pesticides during storage and transportation of apples, and the content chemicals remain on the surface of apples for several days.
Washing with fresh water is also not enough to clean it properly.
Hence, the handler of turtles must wash the apple in hot water, remove peels and seeds.
Then he can offer them to the turtle for eating in minimal, limited quantity.
If the apple contains remains of pesticides, it can cause severe health issues and may lead to the death of the turtle.
To feed the apple, cut the fruit into small pieces and remove the peels and seeds.
Make smaller pieces to ensure that the fruit piece does not choke the windpipe.
You must observe the turtle’s behavior for an hour if you feed an apple to your turtle.
You must call a vet for the examination if there is any sign of dullness or lack of movement.
The vet can diagnose any problem that the apple may have caused or anything else.
You should follow these guidelines strictly while feeding an apple for the first time, at least.
If the apple is not suitable, the turtle may immediately reject it and may vomit.
You should obtain the advice of the vet for the correct diet of the turtle and accordingly feed him.
Best Foods for Turtle
There are various species of turtles, and their food preferences depend on their species.
Usually, for all types of food that we eat, turtles can eat as well, at least in small quantities.
Box Turtle
Turtles from the Bbox species love to eat vegetables like beets, cucumbers, carrots, and fruits like apples, strawberries, and cantaloupe.
If the turtles are in the pond, then they can eat soil and earthworms.
They can also eat spiders, flies, and crickets.
Red-Eared Turtles
These species of turtles like to eat worms and fish, which are mainly protein-rich diets.
They also want vegetarian items like vegetables, cucumbers, and cabbage.
Painted Turtles
These turtles like to eat snails, earthworms, guppies, and tadpoles when they are young.
When they become adults, they can eat almost all types of vegetables and fruits.
Cabbage is a favorite food. They can eat a small number of berries, potatoes, carrots, green beans, and bananas.
You can feed them on alternate days when they have attained adulthood.
Russian Turtles
This species of turtles like to eat leafy plants and vegetables like berries and flowers.
They also want to eat insects and spiders. They are experts in finding their food, so you don’t have to place food near to them.
They roam around and search for it with their skills.
How to feed Turtles
The turtles are generally active in the morning and evening.

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So, you can plan to feed them at this time when they are proactive.
Some turtles become more active after the rain when the weather is a bit hotter.
So, you can feed them at that time.
Turtles living in colder places tend to become inactive during the night when it is cold weather and active during the daytime.
So, you can feed them during the day when the weather is hot and when the sun is out.
If you are keeping them in the garden, you should place them in such a way that they can access the sunlight during the day.
This way, they will feel hot and will be more likely to love to eat food.
Some turtles like to eat in an open area, whereas others love to eat secretly under a shrub or plant’s leaves.
Some turtles eat only in water, and if you bring them outside the pool, they will not eat anything.
When there is enough sunlight, you can feed the turtles in that area.
But don’t put the food in such a way that it gets spoiled due to heat.
You must provide a variety of foods to turtles. It is not wise to give the same taste every day.
The turtle will not be interested in eating the same thing over and over every day.
You can give cabbage one day, and then worms or spiders the next day to provide variety to their diet to change the taste.
They are small but wise animals, and you can train them quickly in a few weeks.
Accordingly, you can mix a variety of food and feed them.
They should get used to all types of foods so that they can get a balanced diet.
Conclusion
Turtles can eat apples but not as part of a regular diet.

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First, wash and clean the apples, cut them into small pieces, and remove the peels and seeds, and then you can feed them.
Besides, they can eat veggies, fruits, all leafy vegetables, and some worms, spiders, and earthworms.