You mean the feeding blocks you put in your tank for your fish when you're out of town? Those aren't very good to use with goldfish, because they will sit there and eat the entire thing until its all gone and then starve the rest of the time. Instead a better solution is to get a friend to feed them for you when you're gone, or get an automatic feeder. Automatic feeders can malfuntion and the food will be fed dry to the fish, so getting someone to feed them for you is the best solution. If you're worried about the person overfeeding your fish, put each feedings worth in a little baggie and label it day 1 morning, day 1 evening, day 2, whatever, and hide the rest of the food, so the person won't be tempted by "starving" begging goldfish.