my dragon

Question
hello my chinese water dragon is opening his mouth after he eats and when I walk by his tank why is that my temp levels are fine but I havent reallly been feeding him any fruits or vegtables could that be the answer to my promblem or is this a problem

Answer
There are hundreds of reasons he could be doing this including "because he wants to," so I can't really say why he is doing so.  If his behavior and appetite have not changed and you are giving him the UVB lighting he needs, I wouldn't worry about it.