24-48 hours from piping is normal for hatching time. I personally get concerned when it takes more then 24 hours, so I usually start to check from there on for movement. You need to occasionally vent the aquarium because is is more airtight then an incubator. It needs fresh air occasionally so the ducks don't suffocate. Commercial incubators always have some air intake in form of small holes in the foam ones or slits in the plastic version. People get to wrapped around about the lock down time and think it is really bad to open it. Excess opening is, but not once in a while is ok. So, if you hear movement in the egg put it back. If not you may need to take a toothpick and chip a little bit away of the shell to see what is going on and to make sure it can breath more easily. Don't go overboard, because you don't want the duck to bleed. This means stay away from the membrane for now.
Katharina