Goldfish and Aquarium Board Articles
Goldfish Nutrition
Part 2: Food and Nutrition

By Betty

The major components of food are proteins, carbohydrates, fats (lipids), vitamins, minerals (ash) and moisture (water).

Protein Protein is needed for growth of tissue and is used an a source of energy. Body tissues are made up of 23 amino acids. Fish can't make 10 of the amino acids. These are called essential amino acids and must be supplied by the diet. Proteins should be a complete source of amino acids and should be digestable (plant sources of protein are often incomplete and less digestable). The essential amino acids are - Phenylalanine, Histidine, Isoleucine, Leucine, Lysine, Methionine, Tryptophan, Valine, Arginine, and Threonine.

There are various recommendations as to how much protein is needed:

I generally aim for around 50% protein in my gel food (based on weight of dry ingredients) because the vegetables contain protein that is less digestable and the gelatine doesn't contain all the essential amino acids. If feeding fresh foods, I feed one part protein to 3 parts veggies.

I use fatty fish in my home made gel foods because they're higher in essential fatty acids: e.g. mackerel, herring, salmon, whitefish, sardines, oysters, lake trout, albacore tuna. Shrimp, krill and live foods are also good sources of protein.

Other Protein Info:

Lipids (fats)
Lipids are a source of energy and are stored in the body for future use. Lipids are also important components of cell membranes, nerve cells and some hormones. Essential fatty acids (n-3 and n-6) have to be included in the diet because goldfish can't make those themselves. They are often called Omega 3 and Omega 6 fatty acids or linolenic and linoleic fatty acids. These essential fatty acids should comprise at least 1% of the diet.

I shoot for a mix where fats makes up 5-10% of the diet with Omega 3 and Omega 6 fatty acids of at least 1%. Good sources of essential fatty acids (grams of omega 3 fatty acids per 100 grams of oil) include: flaxseed oil (53.3g), salmon oil (32.3g), menhaden oil (23.2g), sardine oil (22.1g), cod liver oil (18.8g), and fatty fish (e.g. mackerel, herring, salmon, whitefish, sardines, oysters, lake trout, albacore tuna).

Carbohydrates
Carbohydrates make up 3/4 the of the mass of plants and can be broadly classified as sugars, complex carbs, and fiber (undigestable carbs). Glucose is the end product of carbohydrate digestion and is absorbed from the GI tract into the blood. Feeding a diet high in simple sugars can result in high blood sugar in goldies.

Goldfish don't have the digestive enzymes to break down some carbs that are found in legumes (e.g. soy), however, bacteria in their GI tract can digest these starches and this releases gasses which can contribute to bouyancy issues. Sprouting the seeds prior to feeding reduces the amounts of these starches present in the seeds. Heat treated starches are more digestable.

There is some controversy over whether goldfish need carbohydrates in their diet. Given their natural diet, I believe they do need carbohydrates in their diet--primarily digestable carbohydrates (not simple sugars) and fiber. Digestable carbs spare protein for growth (tissue building) and fiber may contribute to a healthy digestive tract because food isn't just sitting there in the digestive tract.

I generally choose green and red vegetables that are highest in vitamins, carotenes and minerals and low in sugar. e.g. mustard greens, turnip greens, collard greens, spinach, endive, seaweed, kale, chard, broccoli, lima beans, green beans, etc. and feed aquatic plants (e.g. duckweed, azolla, salvenia, etc) or hair algae daily.

In my gel foods, I shoot for a mix of carbohydrates that is mainly digestable carbs and fiber, with 5% or less of the total carbohydrates that are simple sugars.

Vitamins
Vitamins are needed for enzymes to work and are essential to breakdown of carbohydrates, protein and fats into energy and the formation of body tissues. Some vitamins can be be synthesized, but most are obtained from the diet. They can be further classified into water-soluable vitamins or fat-soluable vitamins.

Water-soluable vitamins have a major role in growth, physiology and metabolism. The B complex vitamins are thiamine, riboflavin, pyridoxine, pantothenic acid, niacin, biotin, folic acid and vitamin B12. Choline, inositol, ascorbic acid (vitamin C) are other essential water-soluable vitamins. See Fish Feed Technology, Chapter 6. Vitamins, for specifics on the role each vitamin plays and symptoms of vitamin deficiencies.

Water-soluable vitamins are excreted when there are more in the diet than fish need.

Fat-soluble vitamins are vitamins A, D, E, and K. Fat-soluable vitamins can be overdosed which can cause health problems.

Minerals
Minerals are involved in a wide range of functions that include formation of bones, osmoregulation (control of water balance between the fish and the water), acid-based balance of the blood, gas exchange, energy transitions, muscle activity, cell membranes, etc. Some minerals can be obtained from the water, however, others must be obtained through the diet. The essential minerals are calcium, phosphorus, sodium, molybdenum, chlorine, magnesium, iron, selenium, iodine, manganese, copper, cobalt, zinc, fluorine and chromium.

Also, some vegetables contain oxalic acid which may interfere with the absorption of iron and calcium in foods.

Other
Carotenoids are a family of pigments the fish can't make themselves and are obtained as part of the diet. These pigments result in red, yellow and orange colors. Fish have cells called chromataphores. Those cells convert lutein and carotenes into astaxanthin which is the red pigment.

Sources include: shrimp, krill, spirulina, marigold flowers, paprika, sweet red peppers, yams, carrots, pumpkin

Commercial foods
In general, when you look at the nutritional breakout of commercial fish foods, the percent of each nutrient is based on the total grams of food (including moisture/water). This is somewhat misleading because water provides no nutrients. They also may not provide a complete nutritional breakout. For instance, some old goldfish flakes I have sitting around list: 42% protein, 8% fat, 2% fiber, 6.5% moisture, That adds up to 58.5%, so they aren't listing 41.5% of the nutritional content of the food (ash and carbohydrates). Note the low fiber content. Commercial fish foods typically are low in fiber to reduce the amount fish poop. That's great for reducing the amount of poop in the tank, but I'm not convinced it's great for the fish digestive system.

Fish food manufacturers heat treat soy, wheat and corn to make the vegetable protein more digestable because it's a less expensive source of protein. Often on food labels you'll see separate ingredients listed like corn meal, corn gluten, corn middlings, etc. That's called ingredient splitting and is done so they can list the fish/shrimp-protein as the first (largest) ingredient when in fact it's not.

Soybean meal is often added as a protein source, however it has high levels of a certain type of starch that goldfish don't have the enzymes to digest. They do have bacteria in their intestine that can digest the starch, however that can result in gas production.

Commercial foods should be stored in a cool location (60F or lower) in containers that don't let light in and which are airtight. They should be fresh because oils can become toxic (rancid) and vitamins will be lost over time. Since commercial pellets and flakes are usually low in moisture content, a common recommendation is to soak the food before feeding so that it can absorb water and expand prior to being eaten. This may cause vitamins to leech out of the food. Soaking the food in a vitamin mixture may counter this problem.

I don't believe that a diet composed totally of commercial pellets and/or flakes is healthy for fancy goldfish. Fish food manufacturers are out to produce the cheapest food they can make, and that means adding less digestable heat treated vegetable proteins. Given that fancy goldfish are predisposed to bouyancy issues because their swim bladders are all squished up in their rounded bodies, feeding some types of starches typically contained in commercial pellets and flakes can result in gas in the digestive tract which can make staying upright more difficult. Unlike with pellets and flakes, in a natural setting, most food that goldies would eat would be high in moisture and they would be grazing on various small water creatures, plants and algae which contain lots of fiber and digestable carbs. If you must feed pellets or flakes, read the ingredient list and look for pellets that contain the most fish/shellfish proteins and suppliment with fresh veggies and protein.

Mazuri makes several good aquatic gel foods that are easy to make. If your goldfish can not tolerate commercial foods (is having gassy poop and bouyancy issues), I'd recommend Mazuri Aquatic Gel Diet (5M70), the Mazuri Aquatic Gel Diet w/Krill Meal & Astaxanthin (58LK), or the Mazuri Herbivore Aquatic Gel Diet (no corn 5ZJ3).

A more natural diet
Given, the natural diet of goldfish, I believe it is best to feed high quality commercial foods only sparingly along with homemade goldfish gel food and a mix of fresh and live foods. Multiple small meals are better than fewer large meals. When feeding fresh foods, I believe it is best to feed one part protein and three parts vegetables. For very young goldies or for conditioning goldies for breeding, you could increase protein levels by feeding 1 part protein to 2 parts veggies. You can find my gel food recipes here and here. I also recommend feeding a variety of foods to try and make sure you cover the nutritional requirements and because it is more like their natural diet. Since I feed few pellets or flakes, my goldfish get close to 10 different vegetables/plants and two types of fish/shellfish protein daily. See the GAB Goldfish Diner for more ideas on healthy foods for goldfish.

There are a couple of sites online where you can look up the nutritional content of foods. I use the USDA Nutrient Database to pull nutritional content of various foods to use when working up the nutritional breakout of my home made gel food. Here is another site that will let you sort foods by their nutrient content and let you click thru to the nutritional breakout of specific foods or search for specific foods.

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