Both of the turtles can get up there. They just dont seem to like it. I've still only seen Nibbler stay up there for very long. I'll trick him up there with some treats. He jams all of them in his mouth and runs back to the water usually jumping right on top of Sheldon, who doesnt even come up for treats. Sometimes we'll see them on the ramp, but not in the basking area. Pictures of the ramp angle can be seen here
viewtopic.php?f=6&t=15260&start=285 towards the bottom of the page. We have a reptile carpet that they can grip pretty well. We've also tried making the basking area more secluded (fake plants against the walls) so they feel safer basking, but still neither will bask. Suggestions?