How can I tell that the water needs to be deeper? Simple. The rails on the turtle dock in the picture are 180mm long. The top suction cups are approximately 50mm below the top of the tank. This means that the water level could easily be raised by 150mm.
Turtles prefer deep water. So, in my opinion, a tank should be deep, not shallow. In addition, the greater volume of water means that urine, faeces and food waste will be diluted, not concentrated. Put a piece of wire above the dock so that the turtle cannot climb out.
Have a look at the Frequently Asked Questions section of my web site. There's information there on how to tell is a turtle has been overfed.
I know that several people have told you that they think the turtle is attractive. They are entitled to their opinion. In my opinion, your turtle does not look normal nor healthy.
My advice is to stop feeding the frozen turtle cubes and turtle pellets. There is very little in these foods that are nutritional. The fat and red meat in the frozen foods cannot be processed by Australian turtles. If you keep feeding these foods to your turtle, it will eventually die of renal failure. These is some information about correct diet in the Frequently Asked Questions section of my web site.
Both Peter and I suggested that you go to
http://pets.groups.yahoo.com/group/AustralianFreshwaterTurtlesandFrogs/ for some additional help and advice. Did you find that site helpful?
Regards,
Michael.