I'm kinda silly so I usually shut down my system when feeding, especially in my cube as the scooter and mandarin are very slow eaters.
In my 125g I tend to onlyshut it down for feeding if I'm alos changing a filter sock or some other maintenance task. My goby def prefers it too, if Iput my turkey baster in full of food he goes to the end and tries to suck it out. lol