fat-tailed gecko has a white tail

Question
I bought a fat-tailed gecko just about a month ago.  This is our first lizard so I am not very educated in them.  2 days ago the lizard began to have white on his tail.  It looks like a fungus, but I didn't know if this is what happens when they shed.  The white is beginning to work its way up the tail,  towards the body. The only way I know how to explain what it looks like is that it looks like the calcium powder I put on his crickets...but it's definitely not that.  The lizard is eating %26 seems to be feeling ok, but I need to know if this is normal or if he needs a trip to the vet.  

Thanks for any advise you can give,
Brooke

Answer
Hi Brooke,

It is always hard to give advice based on description alone but I doubt what you are seeing is anything to worry about. Fat tails are not prone to fungal infections and I suspect that what you are seeing may indeed be the start of the shedding process or that area is being rubbed (not enough to cause actual skin injury) on some cage furnishing as he moves around.
When reptiles prepare to shed, a layer of moisture and air forms between the old and new skin which give them a grey/white appearance.
With no other signs of problems I would wait until he does complete a shed cycle which I suspect will resolve it. Fat tails will often eat their old shed skin so you may not see much discarded in the cage after he is finished.