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Blog 2017 – 8: Food, Floating, Fry, and Future by Gary Hater

Above, Veiltails must be fed enough pellets to develop a deep body before the age of one, or they cannot manage their tail weight.

Prepared foods are used by almost all fish keepers. We have a few ambitious fish chefs making gel food their dominant feed of choice, most of us are using pellets first and gel and frozen foods as a supplement. As you watch, listen and post on various web sites and face book sites, I am always amazed how some people are so zealous about food. They like this method, or that food, or a specific brand that they believe is far superior and discretely imported. In some ways, it is a lot like people defending their favorite beer or bourbon as being the best. Often, not a rational reaction, and sometimes very wrong based on the nutrition supplied.

If you go to almost any of the big fish supply places, web sites or catalogs you find dozens of brands with all kinds of variations of food. For many people, if it is the “in-thing” that is what they have. For others, they tend to take the most economical approach, and lastly some keepers just must convert their fish into a food source that fits their lifestyle. For most commercial foods this works out, for some not so much. As compared to humans, goldfish are relatively short lived, generally less than twenty years. For glass tank hobbyists, life expectancy is often less than a third of this. A good resolution this year, put your fish on a healthy diet.

Let us discuss the key components to guide you in reviewing food options;Major Diet CategoriesPercent of total weightProtein30 to 62Fat4 to 15Phosphorus< 1Fiber3 to 5Ash5 to 25Amino Acid SupplementsAugmented for incomplete protein sources


Protein ranges from very low values in things like fall wheat germ diets for koi and very high in some growth foods. Three things to consider are; is the protein soluble in water and does it dissolve or float away, how the protein content directly effects the ammonia produced by your fish (higher the protein the more water you must change), and is all that protein digestible.

Typical sources of protein in the fish food business are;Protein sourceCommentsWhole fishWhole large fishFish MealFish parts and small fish driedSquid MealDried whole squidFish OilOil extracted from MenhadenShrimp MealGround whole shrimpKrill MealOcean krill ground upFeather MealHydrolyzed for digestibilityGlutenAlso, used as a binder

When you look at these various sources of protein remember goldfish do not have stomachs, where bacteria work on the eaten food and help to break it down into usable molecules. There are numerous internet articles from the area of commercial aquaculture that question the digestibility of feather meal and gluten.

Some of my favorite foods include menhaden oil, the fish like the flavor and eat it readily, great as a brine shrimp weaning food, but if it sits very long in the tank you can see the oil as a film on the top of your tank and it will slime over sponge filters.

My favorite proteins are whole fish, krill meal, squid meal, and fish meal. I put up with some gluten as it seems to necessary to get good binding when the pellets are manufactured.

Fat or Lipids:

With the proteins, you get some fat, and in other cases, manufactures use oils as a flavor enhancer and a binder. Some fish like trout demand a high fat diet about 10-15%. Goldfish do great when they are young with high fat diets, but if continued into adulthood, the fish get all round, suffer from fatty liver and often never breed. A good concentration of fat for adults is 6-8%.


Phosphorus is the major plant nutrient controlling algal growth in fresh water environments. It is also important in fish for muscle and perhaps wen development (this is just an educated guess). Most fish foods range from 0.6-1%, one I currently feed is 1.8%.


So much of the internet discussions often talk about fiber, and 3-5% seems to be the normal range. The aquaculture industry suggests that fiber in the 8% range is abnormally high for most fish. Think about this, in the wild state or in outdoor ponds, goldfish are sight hunters when they see micro crustaceans and insects, but most of the day is spent grazing on algae and insect larvae growing on the bottom. Fiber, as in plant fiber, doesn’t exist in the wild state. Of course, modern day goldfish have short bodies and may need more fiber accordingly.


This is the residual left over after digestion of the plant materials. High quality fish foods typically have 3.5-6% ash. In talking to several professionals in the industry, high ash content suggests that calcium carbonate (agricultural lime) may be added as a key mineral or just a pH adjustment and filler to add weight to the feed mixture, you’ve got to remember pellets are sold by the pound after all. Also, if the protein sources of the food you are using are predominately fish meal, and you have a high ash content, you most likely have a fish meal that is lower quality and/or mostly fish bones.

Amino Acid Supplements:

Lysine, Methionine and Cysteine are key amino acids needed for proper growth and in the case of goldfish, most likely wen development. When these amino acids are in the listed ingredients, you can presume that the formulator understands they are needed in the diet and thus also realizes some of his protein amounts and types tend to end up with deficiencies in these amino acids after digestion.

Above, Small fish often require high protein and fat diets when they are small to get the proper shape.

Ok, so next time we are going to compare labels and help everyone get a grasp on what we are reading about. When we get done, some people will be pleased with their choices, some will question why a certain brand is $30 a pound with subpar ingredients, and still others will put their fish on a diet.

Read labels and ask questions in 2017!

For bonus reading you might want to check these links out from the University of Florida to help guide our next discussion:

  1. “Interpreting a Fish Food Package Label” – Frank Chapman and Richard Miles

  2. The Benefits of Fish Meal in Aquaculture Diets” – Frank Chapman and Richard Miles

Both are yummy reads!!!

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