The shell of a Red Ear Slider should be hard and relatively smooth. The carapace should be dark green and the plastron should be bright yellow. Recently hatched RES will have a slightly soft carapace that is a lighter green shade. The most common factors that cause shell problems are related to water (lack of quality or appropriate basking area), diet (lack of calcium, excessive protein) and lighting (lack of UVB). While most shell diseases are preventable, they do occur despite our intentions and efforts. These conditions and injuries often take a long time to heal properly and may require intensive care.
It is highly recommended that a herp vet inspects and treats any injury to the shell. A drop, a fall, an animal attack or some other trauma may result in damage to the shell. Whether it is a crack, a hole or missing scutes, this is a complex problem that needs immediate attention. The risks are shock, infection, shell rot, organ damage, physical disability, excessive suffering and death. If there is bleeding or sizable damage, then the situation is even more urgent and medical attention should be sought quickly. Refer to comment on trauma.
This coloring on the skin, on or between the scutes, on the carapace or on the plastron can be an indication of septicemia (blood poisoning). If your turtle has had a previous illness, infection, injury or improper habitat, it is possible that is has developed into septicemia. Consult a qualified veterinarian regarding appropriate testing and treatment.
It is normal if there is a small amount of algae on the shell, but it is not a necessary condition. It is usually seen on wild turtles or RES kept in outdoor ponds. Most captive RES that are kept indoors have little or none. Algae should be easy to remove if the area is wiped down with a towel or gently scrubbed with a toothbrush and water. Adding a pleco, an algae eating fish, is not a reliable way to control algae on your turtle or in your tank. A pleco will become a potential meal itself and contribute to the waste added into to the water.
Spots that are white or discolored can either be a bacterial infection, fungus, shell rot or mineral deposits. Bacterial and fungal infections can develop from a lack of water quality and inadequate basking. They can start in one particular area and gradually spread outward. These conditions are often contagious and your turtles would require separation during treatment. While there are off the shelf treatments available, you will likely need stronger and specific prescription medication.
Mineral deposits can form if you are using hard water. The excess minerals in the water build on the outer scutes. The development would affect all areas of the shell. If that area is still hard but lighter in color, it is possible a scute is beginning to shed. An air pocket forms under a scute, usually starting at the edges and gives it a golden appearance.
A white cotton-like coating or patch over the shell may be a fungal infection. Fungus may appear in varying degrees of whitish to brownish color. Inadequate filtration and lack of basking greatly contribute to this condition. If this condition is caught early, it should be easy to treat once you provide a proper habitat. A commercial product such as Repti Turtle Sulfa Dip (sodium chloride, sulfisoxazole andneomycin sulfate) allows you to prevent and control external bacterial diseases and fungal infections. If the condition is excessive or does not improve, then you should consult a veterinarian for an appropriate diagnosis and medication.
A build up of minerals on your turtle's shell is another water quality-related condition. Having hard water - water that is high in dissolved minerals, specifically calcium and magnesium - will lead to this whitish build up all over the shell. This is not a threatening condition but it should be addressed. Refer to the hard water section regarding solutions.
Overfeeding leads to an unhealthy large intake of protein and fat. This intake leads to rapid growth, which can cause shell pyramiding. Too much protein can also cause internal organ damage like kidney failure. The scutes on the carapace are not smooth as they should be and appear in a pyramid shape. There are varying degrees of severity, and the areas between scutes may not have their normal strength.
This is a completely avoidable situation. The diet really needs to be corrected and treats or anything carrying large amounts of protein should be reduced. Avoid giving in to the begging and make sure no one is offering additional food. If not immediately corrected, pyramiding is a permanent disability.
Over a period of time, the scutes will begin to shed. This is completely normal and you can notice the process when their appearance begins to lighten or become a golden color. This is due to the air seeping between the new and old scutes. It should not be necessary to help or force the old scutes off, especially when there is a proper basking area set up. It is important for your turtle to be able to regularly dry off completely. Without proper conditions, your RES will retain scutes (dysecdysis), which can lead to an infection.