Suction Cup

Suction Cup
Why is my tortoise trying to mate with a vacuum?

I have a turtle yellow bellied slider in a 55 gallon aquarium. There is a dock turtles in the aquarium out the side vents. My turtle has a mating dance with the suction cup on the wall where it moves the front paws to his face in it. It is my lonely tortoise? should have another turtle so that it can mate with her, or should I continue to put you in the windy movements?

The "mating dance" also done to claim dominance over the other turtle. Ignore that, I'm sure the suction cup.