You should try night crawlers from a petstore.Also try the floating reptile sticks.Crickets are also a nice treat.
As far as the goldfish being with the dwarfs goes;yes it will pig out on the food that was intended for the frogs.Also goldfish produce a significant amount of ammonia compared to tropical fish.The frogs may hide more often as well.Even if the goldfish is not aggresive just because he is bigger than them.