My puffer used to be more active when young. Now that he is bigger, he usually lays in one area of the tank all day long. He might surf the glass for snails. I throw in a crayfish every once in a while and his activity level does increase. This is normal for the puffer to sit and try to blend into the surrounding. When my puff go into hunting mode, then his true hunting strips (very colorful) brightens up the whole tank.