Almost all goldfish keeper observed that goldfish can eat non-stop. So the most popular question is how much I should feed them. The heavy eating habits of a goldfish can surprise even the experienced fish keeper. Most tropical fish will stop eating when they are full. To understand how much food a goldfish needs to thrive, the hobbyist needs to understand “why" goldfish eats as it does.
Goldfish originally came from a temperate climate with four definite seasons. During the late spring, summer, and early fall, food is plentiful. The goldfish eat hardy and store any excess in the form of fats for use during late fall, winter, and early spring when food is scarce and the water is cold. In fact, during very cold periods, goldfish will often stop feeding all together, and can go for months with little or no food. Goldfish are cold blooded animals. As the water temperature drops so does their metabolism. The goldfish kept in an aquarium experiences a state of constant summer so it eats non stop. The excess is turned into stored fats. Pretty soon, you have one big fat goldfish. Overweight goldfish can suffer problems such as constipation, lack of vigor and activity, and a possible early death. To prevent these problems, the goldfish hobbyist should find a food high in carbohydrates and roughage, low in fat, a protein content of 20% to 30%, and feed their goldfish just enough to keep them growing and healthy.
With experience you'll be able to judge it you're feeding enough. Signs of underfed fish are hollow belly, slow growth, or staying too thin. Underfeeding is usually only a problem for the pet shop owner, where the hobbyist usually has a problem with overfeeding. Signs of overfeeding are fish too round looking, sluggish activity, constipation, and swim bladder problems. Another sign of a fat goldfish is a definite swelling between the base of the head and the first ray of the dorsal fin. Goldfish store a large portion of their fat in this area, and it can swell to a very large and noticeable size. Overfeeding is the number one killer in fancy goldfish keeping. As a simple guideline, food should be consumed in no more than 10 minutes. Feeding once a day is usually sufficient. One of the best thing in keeping goldfish is the fact you can enjoy the feeding any time you want; it is the offer no goldfish can refuse except when they are sick. Make sure you don't over doing it.
There are all kinds of commercial goldfish food specially formulated for specific kind of goldfish. Food contain higher percentage of protein is for promoting headgrowth. Some color enhancing feed with the addition of chemical or natural plant ingredient. Normally goldfish can bring out their best color with a balance diet and therefore color enhanced feed is not recommended. Sometimes produce adverse effect. I have seem a beautiful red cap oranda develop red color in the body after being fed with the color enhanced fish food. Consult the label of these feed when purchase.
Slim bodied goldfish can eat just about any type of commercial food whether it's pellets, ground, freeze dried, or flakes. Unfortunately, some of the fancy round-bodied breeds can suffer from constipation or swim bladder problems if they eat dry foods or foods that float. Usually pre-soaking dry food and feeding a sinking food reduces potential food related problems. Flake foods are good for small goldfish. As the goldfish grows a sinking pellet food should be used, as there is less waste with this kind of food.
Brineshrimp, blood worm, daphnia, etc., are all great foods for goldfish. However, they should be used as a supplement rather than a staple.
Earthworm, blood worm, mosquito larvae, small insects, daphnia, duckweed, algae, and other live plants are all excellent live foods for goldfish. If a balance of live food and plant are fed to your goldfish you can expect superior results. So, if you're lucky enough to have live foods available, by all means use them. The only live, frozen, or freeze-dried food I would not recommend is tubifex worms. Due to the polluted environment they live in, they can bring problem to the fish which are better avoided. In general when feeding your goldfish with live food, make sure the food is free of infectious agent.