They will eat much bigger food than you think. Try to feed a varied diet including frozen foods and pellets.
You will soon get used to how much they eat as they stop when full, just like you. Just Hoover up any waste before it spoils. I would feed pups 2 or 3 times per day, little and often. But make sure you keep an eye on ammonia, nitrite and nitrate. Weekly water changes are the key and use dechlorinator.