Feeding Marine Fish and Fish Nutrition Rev 1

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Well-known member
May 22, 2006
The health of our captive ornamental marine fishes is dependent upon the environment and nutrition aquarists provide. A healthy, low or zero stressed fish will heal itself from an injury, can fend off bacterial infections, and resist other diseases through immunity and protein-charged barriers (e.g., a healthy mucous coating). The other leading contributor to their health is their environment (and the stress it creates). In this last group are such things as: water quality, tank mates, tank size, water parameters, etc. Stress will be addressed in another post. There has been a lot written about controling and providing a proper environment, but little can be found about captive ornamental fish nutrition. Part of this lack of information comes from the fact that aquaculture studies have been scarce on this subject, until just the last 20 years.

That is what this post is all about: Fish nutrition. The aquarist needs to take this subject on like a project. The project conclusion is a regime of feedings of the right kinds of foods suitable to the kind of fish being cared for. It is something I and others can reference when there is a concern about the foods, supplements, water additives, and/or feeding regime a poster may be using. I want to be brief (which I didn’t succeed at!), so I will include little background and discussion. However, I’m happy to expand on anything I’ve written. Just post your question in this Forum.

Most of what we know about ornamental marine fish nutrition has trickled down from studies done on marine food fishes in the aquaculture (fish farming) industry. Much work has been done on salmon, sea bass, etc. nutrition, you can imagine, because of their importance as a food fish. However, in the years since the mid-1990's there has been a boon in available information about fish nutrition. Prior to that time, fish farmers only wanted to ‘Feed and Weigh’ their fish. They got paid by the pound and wanted to put weight on them as fast as possible, then sell them.

Intelligence prevailed though. If you want heavy fish, you have to start with healthy fish and maybe even fish that are genetically engineered to take the foods fed and convert it efficiently into muscle and fat. The aquaculture industry has come a long way from the 1930's when meat packing house remnants were used for fish foods.

Quite simply it is either:
1) A source of energy, or
2) Something that is necessary to make the energy.

Trace Elements
Water & Oxygen

Each fish gets its energy or makes its energy using one or more of these nutrients. Food only contains some of the needed nutrients. Fish have different ways of obtaining their nutrients, such as protein, and it has become rather convenient for scientists to group animals based upon how they obtain protein. Let me explain this and the value of the other nutrients.

The building blocks of proteins are amino acids. There are approximately 23 or so amino acids that have been discovered. Of these, it has been found that 10 of them we know are required by our marine fishes. These are the 10 essential amino acids. The fish can’t make all their needed amino acids, and depend upon the correct protein source to obtain them. Depending upon the kind of fish, fish get their proteins from meaty products, the flesh of marine animals, kelp, seaweeds, Spirulina, algae, fish organs, etc. Life forms can be separated into one of three groups depending upon how they obtain their protein. A fish that obtains its proteins only by eating other fish and fish-flesh is a carnivore. A fish that obtains its protein from vegetable matter is a herbivore. And finally, a fish that obtains protein from both flesh and vegetables is an omnivore. (Fishes that are strict detritivores are not covered in this post). The aquarist can't decide on what to feed the captive marine fish until it is known whether the fish is a carnivore, herbivore, or omnivore. This categorization is the basics for deciding what foods are appropriate for any particular fish.

Almost all foods that should be fed to our fishes contain the right kind and quantity of carbohydrates. They are complex chemicals that can be broken down to simple sugars. This is a minor energy source for our carnivore ornamental marine fishes. A fish cannot make its own carbohydrates/sugars. It must come to them in what they eat. But the question really is, "How much carbohydrates do marine fish need to remain healthy?" If you're on a low carbohydrate diet, what marine life can you eat? Almost all of them! That is because sea life contains little stored carbohydrates. However, omnivores and herbivores DO eat algae and algae contains carbohydrates. So these fishes need the veggies in their diet in order to obtain the carbs they need. Failing to feed a tang algae is withholding carbs from its normal diet and although it may enthusiastically eat the meaty foods, the tang is doomed to a short captive life. Marine carnivore fish need very little carbohydrates in their diet. One source of carbohydrates in sea animal life is found in scallop meat.

Most accurately known as lipids, which includes fats, fatty acids, oils, etc. Fish can’t produce their own fats and need to obtain them from what they consume. BUT, like we learned for humans, there are different kinds of fats. The fats our marine fish need are highly unsaturated fatty acids (HUFA) and Omega-3 fats. This we’ve only just recently learned. Incidentally, is a fat fish a healthy fish? Why are hobbyists proud that their fishes are fat? It's wrong. Is a fat human healthy? The marine fish should not be fat. It should have a 'normal' reserve of fat and energy, but it should not be 'fat.'

The (generally) larger molecules I like to call the ‘macro facilitators.’ They help the fish change protein, carbohydrates, and fats into different chemicals that can provide energy. Some are more stable than others. There is a group of essential vitamins for marine fishes. Although they may be added to prepared foods, if the foods have been heated or combined with certain other chemicals, these vitamins can be rendered useless by being denatured (cooked or chemically altered). Most essential vitamins can’t be produced by the fish.

Trace Elements
There are 115+ known elements. Of those there is a group known as ‘natural elements.’ They total 75. The oceans and seas of the world contain all 75 natural elements. Of those elements, scientists have found that our marine fishes need no less than 13 of them to live. They are the 'essential elements.' These elements act, in part, like catalysts to the chemical reactions going on inside our fishes, or are a part of the fish's biochemical makeup, used to carry out life functions. They help convert energy sources into molecules to make energy for the fish and they can do the reverse -- convert stored energy and fats into usable energy. They may be a part of the fish or complexed with other chemicals into tissues. We are sure 13 of them are essential. There may be more (see below).

Fish can’t produce these elements. These elements are often taken in by the fish from the water that surrounds them. Some are ingested (swallowed in foods), some migrate into the fish through their skin, and some pass through the gills, and thus are removed from the aquarium water. There are other processes that deplete these elements in our aquariums. They include skimmers, marine organisms (Live Rock, inverts, corals, algae, microbes, etc.), precipitation and complexing with other chemicals and substrates, and losses due to carbon and other such treatments.

'Normal' water changes in large aquariums can’t keep up with this depletion of the small quantities of the micro elements. Thus, small quantities of element additives put into tank water are needed for proper fish health. If water changes above 50% per month using a salt containing the proper amounts or an excess of these elements is routinely performed, elemental additives are not needed for any sized aquarium. Lesser volume and frequency of water changes for aquariums over 75 gallons will need supplemental additions of trace elements. Small aquariums (under 75 gallons) with water changes of 25% every two weeks will not (generally) require trace element supplements for the fishes.

Water and Oxygen
These things are needed for the fish to make the energy it needs. I won’t elaborate on these, other than to say proper water changes with quality salts is regularly needed. Surface must be broken by agitation or circulation so that gas exchange readily and efficiently occurs.

Take a look at the list. Relate it to the definition of nutrient given earlier. Protein, Carbohydrates, and Fats are sources of energy. Vitamins, Elements, Water and Oxygen are things needed to get the energy from those first three. Ultimately the aquarist is responsible for not only providing each and every nutrient to their fishes, but in the proper quantity, an optimal proportion, and the right kinds.

When it comes to Trace Elements, the recommendation is to supplement tank water with small additions between water changes at least twice a month. The amount? About 1/3 that is recommended on the bottle's instructions.

I won’t further elaborate on Water and Oxygen. They lean more towards the environmental part of the picture. That leaves the other four for closer scrutiny.

Another point to be made. When you find the word "essential" in the above descriptions, keep in mind that they are essential only because people/scientists have found them to be necessary. That doesn't make the others non-essential. Just because scientists haven't discovered how or when the marine fish uses the others doesn't mean they aren't used or needed. This goes for the 'essential' amino acids and the 'essential' trace elements, and the 'essential' vitamins. I don't think that Mother Nature rolled die when she set things up. So perhaps we haven't discovered everything, yet.

These four nutrients (Proteins, Carbohydrates, Fats, and Vitamins) come from various sources. The choice the aquarist makes of the first three needs to be customized to the type of fish being kept. For instance, protein in fish flesh is minimally eaten by tangs. And groupers can’t make use of the protein found in kelp. Remember the divisions mentioned above? Marine fish are divided into three groups depending upon how they obtain their protein. The aquarist needs to sort each of their fishes into the proper group. You have to decide if the fish is a Carnivore (eats meat); an Omnivore (eats both meats and vegetables); or a Herbivore (eats primarily vegetables). (Fishes that are strict detritivores are not covered in this post).

Feeding Frequency
Unless the fish is a strict predator (like a Lionfish), then you should know that the fish eats throughout the day. Most fishes are grazers or nibblers. Large Angelfishes are well known nibblers. Some have been measured to nibble 3 to 5 times every minute on the reef! Ideally they are fed small meals throughout the day just like they eat in the wild. Their digestive track has evolved for this kind of continuous and small intake of foods. Though inconvenient for those of us with full time jobs, the next choice would be three meals per day. In no case should fishes that graze or nibble should be fed less than twice a day. Try to find three times in the day you can feed the fish. Feeding frequency is mentioned in other sections below relating to the foods and types of fishes.

How much to feed
An old question. Professionals measure the foods fed to the captive fishes. This isn't something an aquarist will likely do and sometimes can't, considering all the water that is included in frozen prepared products. If one could measure it, a generic quantity would be to feed about 5% of the adult fish's body weight every day. For sub-adults that would be about 7% and for juveniles more than 10%. Fry would require more. It depends on the fish, its grouping (carnivore, herbivore, or omnivore) and other fish attributes, however.
The aquarist needs to get a feel or an intuitive sensing of when to stop putting food into the aquarium. Usually the fish respond fanatically to the beginning of feeding time. This wares off as they become less pushy and excited about being fed. Some in a community may stop or pick at the food while others may still show interest. When this happens, slow down the amount being added since the entire community is no longer being fed. When those last fish begin to show less interest, the feed time is over. Depending upon the type of fish or the community mix, this could range from 3 minutes to 10 minutes.
My favorite rule is to not add food to the aquarium at such a rate as to have the food 'get by' the fish and become part of the waste. This works well in a community grouping of fishes.

What to feed
You need to get your fish all the proper nutrients in the right ratio. Whether that is through pre-packaged foods or foods you make yourself is not too important. No matter the kind of foods you use, you must add vitamins and fats to your feedings. The pre-packaged foods are either shy some of the vitamins our fish need, or as I’ve described above, may be denatured/ruined by processing. So just don’t bother reading food labels for vitamin or fat contents. Just assume you must add these. They should be added every other day to one feeding only on that day. Strict predators should be given their foods gut loaded with a vitamin or fat, every other feeding.


It’s simple -- our marine fishes eat things from the sea, not the land. They are RAW. READ packaged food ingredients closely. Don’t go by the name of the food or the flashy packaging. If the food is for a herbivore, the ingredient list should not start off with krill, shrimp, fish meal, salmon, or any other meaty products. Not only should it contain vegetables, but it needs to contain raw marine vegetables, not land vegetables. About the only exception to this I’d make is for broccoli flowers. They are nutritious and when blanched (heated slightly to break it down some) are a good food. Don’t use products that say they contain wheat, flour, or land plant or animal products. If you come across a phrase like “plant meal†ask what that means. What kind of plants? Get on the Internet and ask the manufacturer. The same goes for “fish meal.†What kind of fish? Are/were they whole marine fish? Quite often fish meal isn't whole bits of fish, but like meat remnants, are the left over crumbs. If you find a food labeled for ‘herbivore fish’ but it contains a mix of marine vegetables and marine fish flesh/meats, then the food is really only suitable for omnivores. Still, such foods can be used to occasionally feed herbivores.

Food Forms (how is it packaged?)
Fish food comes in different forms, such as: live, frozen, gelled, freeze-dried, flake, pellet, etc. The form has an impact on the nutritional value. The process used to make the food also impacts the nutritional value of the final product. Read more about how to choose the best form here: Different Marine Fish Food Forms

Whole Marine Foods
What do I mean by whole? A whole food is a complete organism. If you have a carnivore or omnivore fish, you should avoid feeding shrimp tails, squid bodies, and other flesh-meaty foods that are part of another marine animal. A carnivore and omnivore can’t live on flesh alone. The carnivore and omnivore needs whole foods. Like a snake consumes the whole mouse: hair, nails, teeth, bones, blood, brains, guts, etc., the marine carnivore and omnivore expects a complete nutrient package. Whole clams, krill, plankton, mysis shrimp, hermit crabs (the only useful purpose for these reef terrorists:D ), raw anchovies, and marine feeder fish are all ‘whole’ seafoods. If you don’t provide your carnivores and omnivores with whole foods, you’ll find over the years the coloration of the fish will change and eventually the fish will succumb to disease or just up and die. This is a kind of stress the aquarist may not always focus upon -- nutritional stress.

If you are feeding Herbivore marine fishes, it is just as important to make sure you are feeding only a small amount of meat protein. But that protein must be whole, as noted above for the Carnivore and Omnivore.

Mysis or Mysid Shrimp?!
Almost any small shrimp-like animals these days are called mysis shrimp. There aren't really 'shrimp' and aren't a member of that family. These organisms are from marine and freshwater sources. The aquarist really wants the Mysid that comes from the sea/ocean. You don’t want a freshwater mysis shrimp species (like Mysis relicta). Read the label. If it isn’t clear, ask. Get on the Internet and find your answers or send an e-mail to the company. As a generality: the Mysid are the saltwater kind. A 'mysis' is supposed to be freshwater. However, packagers of prepared foods often mix the terms. One of the most common of all these saltwater creatures, found off the USA coasts and used in the USA as part of the Environmental Protection Agency (EPA) water quality test is the organism, Mysidopsis bahia. That is where the "mysid" with the "d" has entered into the spelling 'war.' See Foods for Saltwater and Freshwater Fishes. To make things even more complicated Mysidopsis bahia has been renamed Americamysis bahia. So the confusion continues.

Brine Shrimp
Don’t even think about it. Put down the brine shrimp and step away from the package! The only brine shrimp to be fed to Omnivores and sometimes to Herbivores are gut loaded or vitamin encapsulated brine shrimp. Gut loaded means enriched or fed with Spirulina, algae, kelp, fats (HUFA or Omega-3), etc. Don’t feed plain brine shrimp to any marine fish. Do not use gut loaded brine shrimp for Carnivores. Gut loaded brine shrimp is a good choice for feeding omnivores up to NO MORE THAN 15-20% of the meals. Even if you are using gut loaded, vitamin enriched brine shrimp, do not use this as a regular feeding.

Plankton and Krill (Zooplankton)
Plankton are the organisms found drifting on the sea, ocean or on bodies of freshwater. Zooplankton are those organisms in the plankton that are heterotrophic. Most of the heterotrophic organisms are animals, but they also include bacteria, fungi, and other consuming or eating organisms. Since this can come from a marine or freshwater source, the buyer needs to ask if it is marine? Krill are shrimp-like marine invertebrate animals. These small crustaceans are important organisms of the zooplankton. They are sometimes sold separately as Krill. By definition, krill is supposed to be of marine origin and thus, all Krill are of value to feed to marine carnivores and omnivores. Use only marine plankton and zooplankton containing mostly marine animals. Marine Plankton and Krill are very fine whole foods!

This is a particularly fine source of protein and color enhancing nutrients. Spirulina is a microscopic marine algae. But, it should not be formulated to be more than 5% of the feedings (dry weight). It seems that an excess of Spirulina inhibits the fish’s ability to absorb Vitamin K. If you are feeding different foods throughout the day then the content of Spirulina for the 'over all' day should not exceed 5%. So, one food could have 15% spirulina in it if it is fed only once a day and two other foods have no Spirulina.

Foods for Saltwater and Freshwater Fishes
The food can’t be suitable for both types of fishes. Like you don’t buy a single food for dogs and cats, you don’t buy a single food for freshwater and marine fishes. As soon as you see this claim on the label, read the ingredients and see if it been made for one or the other. If it’s for marine fishes, it will have only ingredients from the ocean and seas. The true 'cross overs' are gut-loaded brine shrimp (see below). These are the foods suitable for both on a limited basis because neither saltwater nor freshwater fishes have ever seen a brine shrimp -- i.e., brine shrimp is foreign to both so acceptable to both on a limited basis. :) Freshwater fish are not to be fed with saltwater products. The salt would be detrimental to their health. So when a food is marked "for saltwater and freshwater fish" you can assume it is only proper for freshwater fish. If the product is a saltwater product, like freeze-dried krill, it was made suitable for freshwater fish by removing the salt from the product during the freeze-drying process. This process also removes some other nutrients needed by the saltwater fish. So -- no foods (other than gut-loaded brine shrimp) marked suitable for saltwater AND freshwater fishes should be used to feed your marine fishes.

Almost as important as choosing the right foods is properly presenting the food to the marine fish. After acclimation, having a fish that feeds on foods dropped into the aquarium isn't usually a problem. Still, there are fishes that feed in particular locations in the aquarium. Even though the aquarist is trying to get the new fish to eat -- anything (is okay) -- the aquarist may have to be creative in how to present the food. More on this here: Food Presentation

Fats and Vitamins
There are several different products out there. Find the ones your fish likes and mix and match. Ideally what you choose has vitamins derived from marine sources. Here’s a partial list:
GVH by H2O Life (one kind for foods, one kind for algae) (vitamin)
Selco (fats)
Selcon (fats)
Vita-Chem (vitamin)
Zoe (vitamin)
Zoecon (fats)

One of the most important vitamins and the one that is the most difficult for fish to obtain is Vitamin D. It is also one of the most expensive ones. Whatever vitamin product you choose make sure it is complete.

Out of every 3 feedings, one should include a vitamin supplement and one should include a fat supplement. Frozen foods can just sit in the juice of the supplement for 15 minutes, the excess juice drained off, then fed.

No freshwater feeder fish (e.g., Goldfish, Guppies, etc.)
No brackish water feeder fish.
No feeder fish that are both freshwater and saltwater (e.g. Monos, Mollies, etc.)
No land lettuce.
Minimum of fiber. (Fish don’t need it and it harms them).
15% to 20% carbohydrates.
Less than 90% water (why pay for water?).
Over 10% by dry weight of protein.
Live marine foods fed directly into the aquarium run a risk of introducing diseases and unwanted organisms. Use with caution or after a quarantine process. Particularly important if you feed marine feeder fishes.
Frozen foods and gelled frozen foods are the next preferred to live foods. (See Frozen Foods and Gelled Frozen Foods above). READ THE INGREDIENTS LABEL!
Silversides should be fed only if you're sure they are whole and from the sea/ocean. Did you ever think to ask?
Cyclopeze is a fatty bio-engineered pod and should be fed occasionally. If the size is too small for your fish, you can bind it with some algae gelatin (agar-agar) and make larger chunks out of it. Feeding this doesn't replace using a fat food supplement.
Cyclops is a freshwater copepod. It has its place in feeding to marine fishes because of its high HUFA and protein content. However, it should only be used to feed corals and reef marine life other than fishes, and then not as a sole source of nutrients. Fishes that will eat it are not a concern provided the fish are fed other, marine-based foods as a routine diet.
Bloodworms. They are freshwater midge larvae. Although they contain some fine nutrients, they are not of marine origin. I favor using this product to get a fish to eat, and only one or two meals out of 21 on a routine basis. The true midge larvae are restricted in some places – not allowed to be sold or provided alive.
Black worms are a thin worm often available from fish stores. It is a freshwater fish food and not part of the regular marine fish diet.
Nori. Not my favorite source of seaweed. It is a human product. Too many manufacturers/packers of nori flavor it or treat it with preservatives. Those with flavorings and/or additives are not suitable for marine fishes. Stick to seaweeds, kelp, and algae prepared for marine fishes that eat vegetables.
Fresh macro algae. Nothing better, IMHO. Some can even be found in large Asian supermarkets.

STORE ALL FOODS (even flakes and pellets, except live foods) IN THE FREEZER
Store vitamins and fat supplements in the refrigerator.
Buy only fresh foods and supplements. Buy only small quantities that will last no more than two or three months.

None of these foods replaces the need to supplement foods with vitamins, fats, and the water with trace elements (for large aquariums).

You should know the kind of fish you own or plan to own (Carnivore, Omnivore, or Herbivore). Now that you know the nutrients and some of the nutrient sources you need and where to find them in the proper foods, you're on your way to finishing your project by setting up a feeding regime. [NOTE: I have a table in .pdf that I would like to attach, but couldn't for the time being. This Forum doesn’t allow Word or .pdf attachments. However, if you PM me I will try to send it to your e-mail address.][/font][/size]

VERY IMPORTANT: The following is a generic regime. The aquarist should and can customize the regime and choice of foods to suit any particular need(s), habits, wants, and deficiencies the marine fish might have. Keep within the fish's nutritional needs, regardless of what it might 'like.' Fishes that are strict detritivores are not covered in this post. Notice what is left off this list: what the fish likes. What the fish likes is not to sway what is proper for the fish! :D Lastly: Feed anything to get a newly acquired fish in QT to start eating. No restrictions in trying to get a fish to eat. Once it's eating, switch to the right foods.

Based upon 21 feedings (3/day or 2/day):
This fish expects to eat marine life forms – whole foods.
More than 75% of their foods must be whole marine foods as noted above.
Less than 25% of their foods can be marine animal flesh.
No vegetables needed (but some might sneak in and that’s okay)

This fish expects about 35% vegetables and the rest whole marine life forms.
14 feedings of omnivore food and 7 feedings of vegetables; or
7 feedings of whole meaty foods; 14 feedings of vegetable/meat combinations; or
7 feedings of whole meaty foods; or 7 feedings of omnivore food; or 7 feeding of vegetables -- vary the offerings

This fish expects less than 35% whole marine animals and the balance vegetables. Generally, the older the fish the more it relies on vegetables. So the 35% number should decrease as the fish matures. The following applies to young herbivores (e.g., young tangs, young Rabbitfishes, etc.).
7 feedings of gut loaded brine shrimp, mysid shrimp, Cyclopeze, pods, plankton;
7 feedings of vegetable products (Formula 2, broccoli flowers, Herbivore foods high in vegetable matter);
7 feedings of seaweeds/algae (vary the colors: red, green, purple, brown, etc.) on the clip, attached with a rubberband to a rock, etc.


Mix up the food packagers/manufacturers. For instance you might use frozen gut-loaded brine shrimp, but buy three different brands/kinds of frozen brine shrimp and alternate feeding them to your fishes.

To make all this easier and to provide additional suggestions and options, I’ve attached a feeding table for you to print out. From this table you should be able to draw up your own feeding program. Keep it flexible and include a lot of variety of the right kinds of foods!

Don’t hesitate to ask any question or to make a comment on this (very long) post. Thanks for reading this. :)

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