3 times a day, it's a good amount! Make sure you feed them a variety of foods, different pellets and flakes for example, along with some live foods (they're sold freeze-dried).
But it's a good thing that your fish show appetite
A healthy goldfish is a bit hungry, not staring, but hungry
And if you'd feed them until they simply lose interest in the food, you're looking for trouble. So decide for a certain amount of food and stick with it! The important thing is that the fish get the nutrients needed.