I don't get it. Did you like buy a fish and then set him on the kitchen counter in his bag while you figured out what you were going to do with him?
If it's not already done, there's good info on acclimation and setting up a qt in the "setting up" sticky at the top of the list of threads in this section of the forum, as well as the one Carrie linked. I hope this hippo isn't going in your 75 gallon tank.