Article Index
Basic Fish Nutrition
Understanding Labels
Are Fish Omnivorous?
Protein-The Building Blocks
Lipids-How Much Is Too Much
Preservatives and Why They Are Necessary
Spirulina and Vegetable Matter
What Constitutes a Superior Fish Food?
Bibliography and Recommended Reading


Feeding fish might seem easy, but it is actually one of the most difficult things to teach. In my 35 years of being in the commercial fish business, I have rarely run across an employee who knows how to feed fish properly. It is necessary to have the sense of awareness not to overfeed or underfeed. In some ways it is as much an art, as it is a science. The first rule of thumb is: when in doubt, underfeed! If necessary you can always rectify the situation later by increasing the feed amount. However, if you overfeed, then eventually you can run into some serious problems.

While most hobbyists usually overfeed their fish, there are also those that underfeed their fish to such an extent that their fish actually look anorexic. Many reef keepers are guilty of this due to phosphate and nitrate concern. If the fish is truly fat, simply withhold food and feed less. If the fish is too thin, simply feed more. A hobbyist should know that he or she is in control, not the fish. A healthy fish will always beg for food, but if the fish shows no interest in food, chances are you have a big problem. Either they are sick, or in very bad water conditions.

When you feed pellets, the correct size is very important. Large fish can eat small pellets, but if the pellet size is too large for the fish, they will usually spit it back out, or expel a large portion of the pellet into the water column while chewing. The key is to use a pellet size that allows the fish to swallow it whole. If you keep a mixture of fish sizes in the same aquarium, you can mix different sizes of pellets to ensure that all of the fishes receive their fair share.

Another common mistake by some hobbyists is to pre-soak their pellets, in the misguided belief that this will aid in digestion and prevent swelling of the pellets inside the fishes gut. This is nothing more than an urban myth created by those that simply do not understand the amount of enzymes and gastric acids that are released by most fish when they consume food. Those hard pellets turn into soft mush in a very short period of time! If a pellet food causes gastrointestinal issues in a fish, it will usually be due to the use of poorly digestible ingredients, such as excessive amounts of grains and grain by-products, not from the food swelling up inside the fish's stomach. Most importantly, when you pre-soak pellet food, you are allowing nutrients and water-soluble vitamins and minerals to leach out into the water.

Other Important Nutrients

In recent years Vitamin C has been discussed extensively while other vitamins that also play a key role in the overall health of aquarium-raised fish seem to have been forgotten.

Vitamins—such as A, D2, D3, E, K, B6, B12, Thiamine, Riboflavin, Pantothenic acid, Niacin, Biotin, Folate, Choline, Myoinositol—and minerals—such as Calcium, Phosphorus, Magnesium, Sodium, Potassium, Chlorine, Iron, Copper, Zinc, Manganese, Selenium, and Iodine—also are all essential elements in a well-balanced fish food.

Unfortunately many hobbyists are simply uninformed about the vital role that all of these nutrients play in a fish's diet. Using the mineral copper as an example, many people still do not understand that copper is an essential trace element needed for all living things, including fish. It is a component of numerous enzymes and is essential for their activities. Even natural seawater contains Copper (some in the form of copper sulfate), yet many hobbyists are still often concerned about its presence in fish food. Interesting facts: in water, at a rate of 0.8 ppm Copper sulfate is toxic to almost all fish, but Copper sulfate present in fish food can be as high as 700-1,000 ppm with the only symptom in some species being growth retardation. Anything below 665 ppm did not cause growth retardation in either Coho Salmon or Rainbow Trout. Copper toxicity via commercial fish foods, where only trace amounts are used, is a non-issue, even in sensitive reef systems.

Garlic is another key ingredient in quality foods, and when the correct inclusion rate is used, this single ingredient can play a major role in the long-term health of your fish.

While a manufacturer may use this ingredient to enhance the overall palatability of their food, its main purpose in a high quality food will be for its anti-parasitic properties. I have personally been using garlic in my farm feed for the past 15 years, and while I have never set up a controlled study to chart the exact cause and effects of this single ingredient, I have noticed a drastic drop in disease in my ponds since implementing garlic in all of my feed. Since adding garlic, I have not had a single case of "Florida Deep Well Disease" (disease caused by pathogenic bacteria Aeromonas sp. and Psuedomonas sp.) in any of my ponds, vats, or aquariums.

Over the years there have been a number of studies involving the use of garlic in fish food and the anecdotal evidence with regards to feeding fish allicin complex (the active ingredient in garlic) to rid them of parasites always appeared to be quite strong. As of 2006 there is now some recent science to back these earlier claims up, with one of the largest in-depth studies to date. In this particular study the inclusion of garlic at a rate of 3% was shown to increase the overall digestibility of protein, carbohydrates, and fat, as well as to lower the total bacteria count within the intestine, muscles, and water column. It was also found to enhance fish tolerance to environmental stress.

In many ways, fish food is like an interweaving basket, remove one strand, and the whole thing can unravel. There is no one single ingredient that has more value than all others, each and every ingredient used to make up a premium fish food is vitally important to your fish's long term health. More and more evidence has proven that many common fish ailments such as lateral line disease in Surgeonfish, hole in the head in Angelfish, and fin erosion in Tangs, are almost always nutritional issues.