My Buddy Franklin

Originally a gift for my niece when she was little, he’s probably around 7-8 years old now. Second photo was drawn by a nice girl I met online. I seemed to have trained him to believe that my presence alone means he’s getting fed. He follows my pointer finger around anywhere I want him to go and he loves a nice toothbrush scrub. Still I am curious as to how I can entertain him more in his tank. All I have in there now is a hollow log that’s he’s had since he was little and a floating dock. What kind of toys would make an adult red eared slider happy?