Hello gogo974,
 
can you please tell us in which position you have installed the radiator in your case.  Do you installed the radiator in a place lower then the pump or higher ?
When you installed the radiator in a place lower then the pump, then the AIO is making the aquarium sounds because the air that is at factory inside the AIO (because hot water expands, so they can´t completely fill the system with water) get moved by the pump and wants to go up and start building a airbubble at the highest point that in this case is the pump and the pump can´t move the air out of itself and the aquarium sounds started and stay the whole time.
 
You have to install the radiator higher then the pump and then the airbubble moves out from the pump to the highest point that is now the radiator. After a short time the aquarium sounds gone away and you will be a lucky owner of a titan x hybrid and have a lot of fun with this fine piece of hardware ;)