I have one RES that spends a lot of time basking and another that spends a lot of time under water hiding behind one of the decorations in the tank. It has been that way the entire time I have them (a little over 2 years). The one that hides will bask from time to time, but when he was hiding he was always alert and awake. Lately, he's constantly sleeping during the day when he's hiding. He still seems OK when it comes to eating and other health related appearance issues, but he's almost always sleeping and much less active than he used to unless it's feeding time.
I have my new 75 gallon tank for about 2 months and that's when it started. In the smaller tank he had a favorite sleeping spot he would go to every night. I tried to recreate it in the new tank, but he doesn't like it. He more or less sleeps in different spots all the time and moves around a lot at night.
Should I be worried at all about his lower activity level and sleeping?

