Singing, dancing, doing the occasional backflip, saying "hey, dude!" a lot and eating pizza?
No, seriously, a 'happy' or at least content turt will be bright-eyed and alert. They will pay attention to what is going on around them, and may even be quick to jump to cover or the water- it's not stress, just a healthy concern for safety and security. They will bask and feed regularly, and will explore their enclosure. Hope that helps.
i like to think mine are happy when there watching whats going on and chilling out on there basking dock with as much out in the sun(light) as possible but i guess its pretty hard to tell if they are happy or its my wishful thinking
yep my RES went savage last night and attacked the two relative giants in the feeding tank...he is only 6" comapred to them but i'd never seen them retreat like that before..the dry docking is definitely making them more cranky.