Bullen beißen Grubenschnitzel

1,2 g Fliehkraft Grubenschnitzel fliegen aus der Kurve
I have few question about my Sliders 4/28/09Hi! I'm Roxel from the Philippines.I got questions for my turtles. I have two (2) Red-Eared Sliders (Grub and Schnitzel) both 4 and a half inch long. Grub is the eating machine and Schnitzel is the stubborn one. One day, I'm cleaning their tank. I put them in a pail for a while. The water is deep for them and as I observe them, Grub can float and swim but Schnitzel stayed at the bottom of the pail and comes up to get some air. I thought there was something wrong with the two. I made Grub sink to the water but still he still floats up. I made Schnitzel come up but he or she(still can't identify the two) sank YET comes up to inhale some air. This is my question: Which one of my turtle is unhealthy/sick? What are the ways (if there are) to make them heal?I'll be looking forward for your reply. Thank You!