I just recently purchased a gbta as well. Here are a couple things that I suggest:
1. Turn off your lights when you put the gbta into the tank and reduce the flow dramatically.
2. Gently place him on a rock and hold him there until he begins to cling to the rock. Once he starts to atach to the rock let him go and he will do the rest. Keep your flow low until he firmly ataches to the rock and then let him have it, but make sure you do not have a ph pointed directly at him.
3. Reduce your lighting period for the first couple of weeks.
4. Do not worry about feeding him.
5. Do not freak out if he deflates, this is normal.
6. Lastly, Maintain water parameters and I would put in some fresh carbon.
Hope this helps.