Thankyou I think this would be the safest option.a strong light source will get a nennie to shift it's position, I usually turn my powerheads off and put one of the LED units overhead where they are and they generally move down. The key is the downward movement. What I then usually do is make sure I have a rock lower down that can be easily moved under the rock they are currently on. They then shift onto the rock I want them on and then can be situated wherever.
Done that before. As it sits on the glass its should be easy.Many have had success with a credit card or bank card too