I just had the same situation as Masonic on Monday. Put in fresh water for my caramel albino boy and 15 minutes later my wife took him out and he was sliming everything. I checked for bubbles from his mouth and nose and didn't see any. I moved him to my quarantine tub and bumped up the temps a little and misted really good just in case. When my wife got home from work he was fine and has been all week. Pretty sure he had just taken a big drink.
Make sure your temps and humidity are good and if he is still showing bubbles from his mouth or nose then get him checked for a RI.
Good luck!