leopard gecko mobility

Question
I have kept two male geckos for 9 years - separated, once I found they were not a pair!I have tried various substrates, but after one developed impaction, have decided to do away with the substrate, and just keep a piece of tissue in their poo corner which can be changed daily. This has worked well in terms of their appetites, which now seem healthier. But over the last few months this gecko has developed a mobility problem, in that he drags himself around, and can't seem to raise his tummy off the ground.this morning I was alarmed to find him upside down. He otherwise appears healthy - bright eyes and coat, reasonably fat tail. He has a heat mat under the tank ( plastic ), and has lived on a diet of black crickets with occasionally waxworms. I have not provided UV as I have heard that it is not necessary. Any ideas?

Answer
Hello Deborah,

Well, most of the time it is not really "necessary" to provide UVB for leopard geckos but it has been shown that they can benefit from low levels of it.
Do you use calcium supplementation on a regular basis?  
You can use felt for substrate so it will provide some protection for him from the undertank heater.  The dragging of his body sounds like he is developing metabolic bone disease.
Can you post a picture of him?

Tracie