Lethargic red ear slider

Question
My RES is usually very energetic,always alert and swimming around the tank. He was always using his basking rock but today I noticed that his movements are slow and he isn't basking. When he goes up for air he slowly floats down to the bottom of the tank instead of swimming. He still eats and nothing seems to be wrong visually. What's wrong with my turtle? This was an overnight change. Help!

Answer
Hi Rose,

I can't really say what's wrong with your turtle, but often when they become lethargic like this there's a respiratory infection going on.  Look for other symptoms such as listing (swimming lopsided), wheezing, gasping, gaping/yawning, stretching the neck out, etc.  If you see any of these signs you should get your turtle to a vet for treatment.  If he doesn't improve within a day or two you should still get him to a vet because ongoing lethargy is generally a sign of something serious enough to warrant vet treatment.  Good luck!