If you like things backed up by science and logic you should definitely join a Facebook group called Bearded Dragons Network. With that being said here's a small bit from a file that they have when it comes to baths for bearded dragons:
"A dragon should not be bathed really. Unless dirty.
And...
Hey everyone,
I recently found out that a 40-gallon terrarium might not be enough for my bearded dragons. I am looking for a 120-gallon terrarium but I have searched everywhere with no luck. Most websites that sell them aren't in business anymore. The ones that are still in business charge an...