What to feed my turtles?

As a new turtle keeper, I always want to try something new for my turtles. I don't really think my lovely turtles will enjoy the turtle food steak very much. I searched all day for right food for turtles. I found the article below. I hope it will be helpful for you guys.

Article source: http://www.turtletimes.com/forums/topic/41568-a-diet-summary-for-sliders/

Providing a Balanced diet for Sliders

The diet of the Red Eared Slider can be somewhat difficult to understand. For the interests of people new to the Slider, and of course its close relatives, I have decided to make this topic. Here I will discuss the most important parts of the Slider diet, as well as certain dietary issues.

For easier reading, I will put general information in Bold, and my own personal comments are given in Italics

The way in which Sliders and other water turtles feed is quite strange. They require the water in their mouths to swallow. Because of this, they should be fed in the water.

The recommended amount to be fed is a portion equal to the size of the turtle’s head. Also, as turtles grow, they should be fed less frequently. Feeding a hatchling daily is fine, but adults should be fed once every 2-3 days. It is up to you to decide when your turtle is big enough to stop being fed every day, but I would estimate around 4", getting less frequent as the size increases.
A lot of people feed their turtles in separate feeding containers to reduce waste and mess. I do this with especially messy foods, but I try to keep stress to a minimum by usually feeding in the main tank.

The main groups of food are:
-  Processed food
-  Animal Protein
-  Plant matter

 PROCESSED
To start with, I will talk about the processed turtle foods, sold in most pet shops. These products are usually comprised of the main food groups rolled into small pellets. Don't let the tub fool you, a lot of them say that they are the only food necessary for turtles and a lot of unwary turtle owners trust the packet. They should certainly not be the sole staple of the slider diet.
However, even though processed foods aren’t a sole staple, they should still be a portion of the total diet offered. A lot of care sheets on the internet, and several books, recommend that the amount allocated to these processed foods should be 25%.
I recommend that rather than feeding an entirely pellet meal every four days, just mix a few pellets in with your daily feeding. I say this mainly because some turtles, especially ones exposed to a pellet-only diet for some time, can refuse other foods, so feeding a pellet only meal could, in my opinion can trigger them to refuse other foods.

There are several brands of commercial turtle foods. Here are a few of the main ones:

ReptoMin by TetraFauna is an excellent product nutritionally, especially in calcium, which is important for turtle's shells and bones. It is mainly made from vegetable extract, fish and derivatives, mollusks and crustaceans, and algae. Most of these are part of the natural slider diet, except the fact they are not fresh.
ReptoMin is the usual pellet I use. I find it an excellent product and it comes in several varieties, including a formula for hatchlings. My Red Ear also seemed to take to them easily after I switched from another brand. Also, they soften quickly enough in water and do not get broken up easily if the turtle does not eat them immediately.

Wardley Turtle Sticks is another brand name I know of. It is mainly made from Ground Corn, and fish, chicken, corn gluten and soybean meal. It has more protein than ReptoMin, but has less calcium. 
I have not used Wardley before, but I know several keepers do. I have heard good things about it, and it is a popular choice, however, it is unavailable where I live.

Sera Raffy Turtle and Terrapin foods are the final commercial food I have chosen to mention. More and more pet shops seem to be stocking it lately. It contains natural foods, such as mussels and fly larvae and is rich in protein and calcium. 
The downside I find with the Sera Raffy brand is that they recommend that you alternate between the different varieties of their commercial foods. This can get fairly expensive as there are several varieties.

All the commercial foods I mention are found in many pet stores. A mixture of these processed foods can be used, but I prefer to stick to one as it's cheaper and guaranteed to be used up within the use-by date.

 ANIMAL PROTEIN
This type of food is important for proper growth. Too much animal protein can cause the shell of a turtle to pyramid, which will disfigure it for life. Most keepers recommend that Sliders should be fed 25% animal protein in their diet. As most turtle's age, they tend to eat more plant matter and less animal protein, so alter the diet accordingly.
Again, I recommend adding a small amount to your Slider's daily meal rather than a totally protein meal every four days.

Animal protein comes in many forms. Some types come with lots of calcium, others with lots of fat, so it's important to be aware of what your little shelled buddy is consuming.

Meats are a good example of animal protein. Beef and chicken are the more common fed to turtles. They both have large amounts of protein, but these meats should be cooked first before feeding to your slider. The downside of beef is that it comes with a lot of fat. Both chicken and beef are also not easy to prepare everyday, unless of course you're cooking it for your own meal, as cooking a pea size piece of either is hard work! Avoid all tinned meats, such as Spam, corned beef, or things like hotdogs, as there's a lot of fat in them.

Fish, shellfish and crustaceans are good natural examples of animal protein. The natural slider diet consists of a lot of aquatic crustaceans, so things such as water snails, prawn and mussels are excellent. Also, they contain high amounts of calcium, important for the turtle's shell and bones. Whether you feed live or dead food is up to you, as live fish can benefit the turtles a lot as they get exercise from chasing.
Minnows, Danios, Guppies and Tiger Barbs are all good fish to have in the tank as Feeder fish. Goldfish are unsuitable as they are too fatty and have a sharp spine in their fins. Please do not be tempted to introduce live clams and crayfish into a turtle tank, as both can do damage to turtles. Also, try to avoid the pet-shop freeze-dried foods, such as brine shrimp, as they are just the 'husk' of the animal with little nutritional value.
I occasionally feed prawn as my animal protein source, but variety is the key. Switch between several types of protein for a healthy Slider! I like to leave a few feeder fish in the tank and skip my daily feeding of animal protein if one is missing, but some turtles completely ignore them! I recommend tinned tuna fish for anyone who cannot get their turtle to eat, as it has a very strong odor that entices sliders to. 

Live insects are good for turtles also, although there are a few things you should know. Insects need to be 'Gut loaded' before feeding to animals, which means feeding them a good meal so your turtle gets a good meal. There are two ways to gut load an insect. One is to use a commercially available Gut load mix; the other is to feed them fruit and vegetables. I like to feed my insects potato, carrot, and bran cereal. Make sure you replace the vegetables regularly though, as they need them for water. There are also several types of insect. Crickets and locusts are good, but the main nutrition area is the juicy abdomen, and some people remove the back legs to stop them jumping, and because they can be difficult to swallow and digest. Mealworms are difficult to digest, and try to get regular ones, not the hormone treated giant ones. Wax worms are full of fat, so feed rarely. Insects and bugs from your garden can be fed too, such as Earthworms and pill bugs (woodlice). Make sure that there are no pesticides used in the area where they are collected.
I like to feed a big locust every now and them without the legs, just watch the head as they can bite, and I usually remove that too. They are also expensive (around $1 each for adults) and noisy, as are crickets. I find mealworms are best bought small, as if they are adults they turn into beetles quickly. Earthworms can contain parasites, so limit them, unless you buy them as reptile food and do not dig them yourself. Frozen fish foods can be fed in moderation. Bloodworm will be readily consumed, as will frozen brine shrimp. They can all be messy, and it is best to feed these in bare-bottom tanks, or a separate feeding container. They are easy to keep for a long time in the freezer, and usually cheap, just allow them to thaw out first before feeding. I feed bloodworm in small amounts in the tank, as the feeder fish eat any excess, but if you are feeding large amounts, try it in a separate container. I feed this protein about once a month.

Other proteins are available for other animals. Dog and cat food can be used. The stuff in the jelly is easier to work with rather than the dry stuff, but they usually contain a lot of fat. 
I don't like feeding these foods, as they are not part of the natural diet, and seem a bit unhealthy to me. They also make a big mess, and dry foods have to be soaked first. My slider didn't seem to like them much either, so I never really use them.

 PLANT MATTER
Plants are very important to the Slider's diet. In the wild, an aquatic turtle would frequently eat aquatic vegetation, so it is important to offer it from an early age. In general, baby sliders may refuse to eat plant matter, and will eat a more meaty diet, but lots of them tend to become more vegetarian as they age. Plant matter should be offered at every feeding even if the turtle refuses to eat it, and having a source of plants in the tank does little harm. It is almost impossible to maintain a planted set-up in a turtle tank, as even hatchlings love to tear up aquatic plants, even if they don't eat them.

I will begin this section with a few aquatic plants that I have had success with.
-Anacharis, the common water plant. Usually sold for cold-water aquariums, it is cheap usually and nutritious. Turtles will readily tear into it, and usually eat it.
-Water Lettuce, provides shaded areas as it is a floating plant, and turtles will take chunks out of it. Water Lettuce can sometimes expensive to buy however.
-Duckweed, common small green plant that can be found on many ponds. High in calcium and provides shade.
Anacharis is excellent, but feeding in a separate container is best, as it makes a huge mess. Duckweed is good, but can clog the filter and dries on the glass looking nasty. I recommend adding a small amount to the tank. The turtle will eat it, or it will grow.

Some non-aquatic plant matter recommended for Sliders are:
-Dandelion leaves, make sure they are not collected from an area that has been sprayed with pesticides.
-Lettuce, not hugely recommended as it has little nutritional value, but avoid iceberg, which is basically water. The best to use is Romaine.
-Collard Greens can be floated in the tank and just left for the turtle to take bites out of.
-Shredded Carrot is good nutritionally, and my Red Ear seems to enjoy it more than other vegetables.
Dandelion leaves are easy food as long as you're sure they're pesticide free. Floating a few leaves or romaine lettuce or Collard greens allows the turtle to play with something in the tank also.

Some plants contain too much oxalic acid, such as Spinach and broccoli, which inhibits the absorption of calcium. Try to stick to greens that have been mentioned for turtles. Fruits can be fed as a treat, such as banana, but only as a rare treat.

DIET ADDITIONS
Cuttlefish bone, available at most pet shops for birds to sharpen their beaks on, should be offered to the turtle. Try to get the unflavored kind, without any seeds or flavoring meant for birds. Remove the hard backing on one side (the side which you can't make an indent with your nail) and float the soft part in the tank. This is full of calcium and the turtle will bite chunks off occasionally. The soft cuttlebone can also be ground into a powder and applied to foods, although it will quickly dissolve in the water. Cuttlebone is cheap, and comes from the cuttlefish (a squid like creature). I buy each cuttlebone for under $0.50
A vitamin/mineral supplement can be added to the foods for a boost, especially if your turtle is lacking a certain vitamin or is unwell. Always follow the instructions on the packet and don't go over the recommended amount.
I add a supplement once a week. I also apply it to meals with not as much nutrition, such as lettuce.

Diet plans:
Hatchling (up to 3-4"):
Feeding once a day, a couple of hatchling pellets, a treat size protein (about 30%), and an offering of plant matter, although the turtle may not eat it. A small 2cm block of cuttlebone placed in every 3 days.

Sub-Adult (4-8"):
Feeding every 1-2 days (longer gaps between meals as the turtle gets larger), 2-3 Processed turtle sticks, a small amount of protein (25% of diet), such as prawn, a large plant section, even if left in the tank for a day. Unless the plant matter is an aquatic plant, remove any uneaten plants after a day. Cuttle bone should be a 3-4 cm block, replaced every 3-4 days.

Adult (8" and larger):
Feeding every 2-3 days, 3-4 Turtle sticks, a medium size protein amount (about 15% of food), such as a feeder fish or prawn, a couple of greens, such as dandelion leaves. A whole cuttlebone (without hard backing) should be floated in the tank until it sinks, then replace it.