OrionN - All the C. gigantea I have seen have longer and more pointed tenticles. They also have a darker, orange or reddish column.
Biggie - Can you just rotate the rock around? I can't see it in the pic, i guess because it is behind the rock, but is the power head blowing right on it. Maybe more direct flow will encourage it to move. Shading it from light will encourage it to move into the light. Basically you have to make it want to move to a better environment. Right now it is happy where it is at, it doesn't care if you can see it or not.