Are Tetra Pond Wheatgerm Sticks suitable for goldfish in an aquarium?

Those would be just fine to use. Usually that's given to pond Goldfish and Koi before they go into hibernation in the Fall, and in the Spring when they start eating again when the water warms up, but this is ok for your Goldfish if they will eat it. You may have to break them up a bit, depending on the size of your fish. These sticks are made for any type of pond fish, and Goldfish ARE pond fish if actually kept in a pond.