Thank you for getting back to me. I can tell that you care about your turtle, but someone - perhaps a pet store clerk - has given you incorrect information on how to care for a turtle. At this point, your turtle is ill. We'll talk more about that in a moment. first, I want to go over basic care and the changes you'll need to make if you want to return your turtle to health.
It's recommended that a baby slider have at least a 15 gallon tank. By the time the turtle is 3-4 years old, it will need a 60 gallon tank, so it's best to get the biggest you can in the beginning. You can also use a large RubberMaid tote. That's not as pretty as a tank, but costs a lot less. Set up the tank so there's a land area and a water area. You want the water to be about twice as deep as the turtle is long. If the turtle is two inches long, you'll want four inches of water.
In order to be healthy, turtles need certain types of lighting and need to be warm. Your turtle is cold. Air and water that are not warm enough can lead to fungal and respiratory infections. Turtles must have a basking area where they can get out of the water, dry off, and bask in very warm light. The ambient air temperature in the tank should be around 75 (24*C) degrees, with the basking area warmer still. Over the basking area there should be some sort of lamp that will take a 40-60 watt incandescent bulb (or you can buy a ceramic light fixture made just for reptiles). If you live in an area that has farm stores, you can buy a metal light fixture made to keep baby chicks warm for just a few dollars. Don't buy the accompanying bulb, however. You need an ordinary incandescent bulb in the basking light. Hardware stores sell similar fixtures as work lights. The basking area should be kept at 85-88 degrees (29 to 32*C). Use a thermometer to be sure. You can adjust the temperature by raising or lowering the light fixture. If your tank is small, set up the basking area at one end - you don't want the entire tank to become too warm. The lights that come with the covers on aquariums are not suitable for turtles. You'll also need a submersible aquarium heater that will keep the water 78-82 degrees (26 to 28*C).
It's extremely important that you buy an additional light that produces UVB rays. A Reptisun 10 is a good brand that does. If you choose another brand be absolutely certain it provides UVB rays. Don't take the word of pet store personnel, but read it for yourself. Full-spectrum, UV, or UVA are not the same thing. I'm putting a lot of emphasis on this because it's crucial to your turtle's health. Without this light, Metabolic Bone Disease (MBD) will develop because your turtles won't be able to produce vitamin D. Vitamin supplements are not a good replacement for the proper lighting. MBD causes a very slow and painful death. UVB bulbs must be replaced every six months as they lose their effectiveness after that, even though they may still look fine. Light that comes through a window isn't sufficient because the glass filters out the rays turtles need to stay healthy.
Turtles are very sensitive to water quality. Even if you change the water every day, it can still contain harmful chemicals. A good filtration system is essential. Water changes are also needed even with a filter.
Feeding is an area where pet stores often give out bad information. Commercial food should make up only 1/4 of the diet. Animal products (meat, earthworms, canned cat food) should make up another 1/4. The remaining half should be plant foods (dark lettuce like romaine, bits of strawberry or melon, etc.)
You may want to look at these sites for additional information on care and feeding.
Your turtle is sick right now, and will need to be examined by a vet. He probably has a bacterial infection, and may have a kidney problem as well. If you don't know of a reptile vet, give me your city (nearest larger town if yours is a small one) and state, and I'll help locate one.
Many times, people get turtles without knowing about the expense involved. If all this sounds like too much expense for you, give me your state, and I can refer you to reptile rescue groups who would take the turtle and care for it.
If you have further questions, or want a list of rescues or a vet, just let me know by clicking on REPLY. There's no additional fee for such follow-up questions, and I'm happy to help. I hope you enjoy many years with your turtle.