Pond turtle supplements are often not needed by most turtles but can literally be a lifesaver for a turtle who seems to be having issues with nutrition.
Nature makes every animal different, just as every human is different from every other. That said, from time to time a turtle may be having some problems with their nutrition. Some turtles naturally suffer from various disorders of the digestive system, anorexia, in addition to many other nutrition issues. They can also suffer from bone problems or shell deformities which can be corrected with additional nutrients which they are having a hard time obtaining from their regular food sources. You may be having a hard time trying to distinguish exactly which disorders your turtles are suffering, so it is always a good idea to seek assistance from a veterinarian who specializes in reptile health.
Some of the more simple pond turtle supplements will be used to encourage turtles to eat. Appetite stimulants come in many forms, including vitamin B complexes which have been shown in studies to generate appetites in all different sorts of animals, including pond turtles. Calcium deficiencies are also fairly common in pond turtles so they may need help in obtaining enough calcium to maintain their best health. If a turtle cannot maintain proper levels of calcium they will suffer from bone illnesses and shell problems. If they do develop issues with their shells, they can eventually suffer a very painful death as their shells help to distribute their body mass and support their internal organs. Vitamins D and C are frequent pond turtle supplements as well. These vitamins can help stave off disease and build the immune systems of pond turtles.
Because turtles are omnivores (creatures which eat both animal and plant resources) they will eat just about anything they come across. This is carried over to pond turtle supplements as well. You will find a blend of proteins (from both animals and insects), fruits, vegetables, and other plant forms, in addition to straight vitamin supplements.
When you have determined that your turtles do indeed need pond turtle supplements, make sure you follow the package instructions to the letter so you will be able to effectively treat your turtle. Their health needs are somewhat complex, but once they heal from their ailments they will be stronger and ready to continue building a strong relationship with you.
Take care of your turtles with pond turtle supplements when they need them and your pond turtles will reward you with a long friendship.