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The foods and feeding of pond fishes for desired results (growth, maintenance, color, reproduction, disease-environmental resistance...) is one of a few sets of major factors in the determining the health of our livestock.
There is no shortage of myth, anecdotal evidence and advice, mis- and disinformation, bizarre practices in the hobby of koi and other cool-water fish keeping where nutrition is concerned.
Many pond fishes are killed off prematurely through mis- and/or over-feeding. Incredibly there is a tremendous body of scientific knowledge concerning carp and other minnow nutrition. This interest is entirely reasonable given the role of some of this family's (Cyprinidae) members occupy in human nutrition, sport fisheries & algae/weed control.
Feeding the "right" foods, in acceptable formats, in appropriate amounts, at proper intervals, under acceptable conditions can/does go a long way to insuring your livestock' health.
This Section attempts to 1) provide a brief overview of current facts, the what and why of nutrition, 2) a glimpse at the role of major co-factors, & 3) some idea of what a conscientious pond-keeper might/should do foods & feeding wise.
I. Introduction: Rationale, Overview
II. A Conclusion:
I. Introduction: Rationale, Overview:
On the face of it, feeding and nutrition of ornamental carp, goldfish, Orfes, and other minnow-like (family Cyprinidae) fishes is a simple matter. They are all opportunistic omnivores, seemingly eating anything and everything offered up to the point of satiation and beyond. Things are not always what they appear.
Depending on your purposeful desires for your livestock; maintenance, growth, color/pattern/conformation development/enhancement, disease control or treatment, what you feed & how you feed can make a very large difference. It is not lost on many people that there exists a wide range of quality in ornamental stock and it's longevity. Along with heritable characteristics, development up to the point at which the stock comes into your care, water/environmental quality and the absence of disease, nutrition is the completion of major determinants of aquatic animal husbandry success.
This Section describes an understanding of the role of foods, feeding and general nutrition in concert with these other groups of factors as an adjunct towards these various ends. It is obvious that no life is possible without adequate nutrition, and no real quality health without proper nutrition. Similarly, of course, your livestock cannot become more than their genetic heritage, developmental history or suitability of their environment will allow/nurture. Proper nutritional practices therefore must be understood as only one of several critical elements, or parts of a puzzle in the production of optimized specimens.
A. Ends of Keeping Pond Fishes:
People "keep" fishes for various reasons; to see if they can do it, because they're curious, "to breed" them, to win prizes/recognition... Correspondingly with their ends, more or less time will be expended researching the best/proper conditions for rearing the stock. Foods and feeding are probably a close second in real costs in terms of time and money after electrical expense for filtration/circulation/aeration for most hobbyists and commercial enterprises. Foods can be quite expensive.
Surprisingly (to me) most people I've met too often feed too much of the wrong foods, shortening the life-spans of their charges, challenging their health and outright polluting their systems. Rest assured, this is regrettable, avoidable and a matter of science: testable, falsifiable hypotheses. Nishikigoi (koi) Cyprinus, goldfish Carassius, and many other historically important species of "carps" have been extensively studied for literally hundreds of years. Though most of these studies have focused on aspects of growth and disease resistance, much is known in terms of color, pattern and body shape development as a function of nutrition. Apparently few investigators/keepers/writers avail themselves of the enormous body of facts, ideas, methods and attitudes that is the body of knowledge concerning pond- fish nutrition. Similarly, the preponderance of mis-formulated foods and their popularity testifies to the state of ignorance/acquiescence of the consumer to this lazy market.
If you are interested in maintaining aquatic life for fun, money, ribbons/trophies or food, you should be concerned/informed as to available appropriate technology for nourishing your livestock at the lowest cost and trouble. So on with it.
Why ask why? Towards what ends do you keep fish? For "fun"?, to "compete" at fish shows, for food...? Depending on your answer(s), reason(s) the question of what to feed, how and how often will differ.
Probably the most common "reason" for feeding. A point to stress over and over is where/whenever in doubt to underfeed. The most healthy stock I've ever examined have done fabulously on "benign neglect". In several areas in Japan and Europe, very expensive stock are underfed to not fed at all for long periods of time, principally winter. More livestock (by orders of magnitude) is killed prematurely or outright by overfeeding and pollution from over- and mis-feeding than all other cumulative sources of mortality. Is this clear to you? Don't overfeed.
Organisms maintained outdoors, unless grossly overcrowded will rarely succumb to starvation, subsisting on "naturally" occurring foodstuffs; insects, algae and associated micro and macro-organisms between sparse "supplemental" feedings.
So why provide auxiliary/external feed at all for general maintenance? There are nutritional deficiency diseases and who really wants to risk scrawny aquatic pets? Offering a regular regimen of fresh and/or prepared foods allows one enjoyment and more control over aspects of the quality, physical and aesthetic of your fishes. How much, how often of what per what type and size of livestock is offered below. Composition of foodstuffs for maintenance is determined by mainly temperature/weather for any given type of aquatic livestock.
To recap: Just keeping your livestock going is what most folks seem most interested in. Towards this ends, getting about the right mix of proper nutrients in about correct proportions without too much "bad stuff" (impurities, biological and not, traces of pollutants, pesticides, parasites...) in an acceptable format (pellets, frozen...) at an affordable rate is what we're aiming for.
For the most part, for most keepers, here we're talking more of the same maintenance diet, offered more frequently. Some increased protein concentration during "warmer" annual conditions has been demonstrated to boost weight gain, but it should be noted that this increased growth may be at the expense of body conformation (shape) and color intensity and pattern. You must decide within the confines of your conditions (& the genetic potential of your stock) how much growth is enough. Is a 12-14" koi fish possible in under two years? Yes. But will that fish live a shorter time than if it took 3-4 years to get that size? Yes; most likely.
How important is food/nutrition in the equation of the making of a Champion? Or a "good" fish from a mediocre one? Depending on whose opinion you listen to, a little to a great deal.
Certainly an organism in your care that has the genetic potential and developmental history up to the point in which you got it is going to be influenced positively & negatively by what you feed, how often. How important are other factors, such as those listed below? Absolutely (!), and yes, just like reality, they (and more to be discovered) all interact with each other to greater/lesser degrees in myriad ways affecting color/pattern.
Must you go nuts trying to optimize/understand your situation? No! Will you go broke paying more for those stupid @#^*| fishes foods than your own? Not necessarily> read on.
Normalcy; is that too much to shoot for? Nah. Along with infectious and parasitic, environmental, and social (!) diseases, nutrition or lack of it is a viable category for health or no.
Some examples: Gossypol from cotton seed oil is an extract being tried out as a human male birth control; it is an identified "problem" molecule in carp nutrition, leading to fatty degeneration and sterility. Cotton seed meal is definitely to be avoided in hobbyist mixes; hence the exclusion of "trout" and "catfish" foods for pond fish.
Vitamin C; as per our nutrition, is required in minute quantities and not produced endogenously in fishes or ourselves. Therefore it's addition in prepared feeds. In the "wild" and most people's ponds this and most other "trace" substances (as opposed to primary nutrients are available as products/by-products of algal, aufwuchs, "stuff" falling in. In high intensity culture systems, vitamin C and other supplementation is indicated.
The atomic and molecular nutrient requirements of fishes are about the same as for you and I. A few fats & carbohydrates, several amino acids, trace elements, vitamins, water and oxygen. Everything else (fiber, ash...) is not usable, perhaps harmful and hopefully "this too shall pass", and not muck up your system.
It's often stated that koi and other commonly utilized cyprinids have no "stomach", a relatively short alimentary canal, that excess protein may harm or "burn them up". Malarkey. They do possess out-pocketings of the gut, pyloric caeca, that greatly enlarge the digestive system's surface area/absorption capacity; though admittedly no acidic stomach. Ingesting "hotter" foods (one's with more protein) will not cause your fish to burst into flame. The same mechanisms for you and I prevail. The facts are that increased concentration of "expensive" components in foods are simply not warranted on the basis of first pass utility, fouling and general cost/benefit value.
Koi do not have "teeth" on their primary bite, but do have smaller "grinding" pharyngeal teeth that aid in sorting and making smaller their natural "target" foodstuffs. Finely divided materials are better than larger for processing and absorption.
If you want to believe in a benevolent creator, study the biochemistry of fishes. You think the space shuttle's are sophisticated, with lot's of back-up systems to provide flexibility? Ha! Carp can do major pathway changes in the face of temperature, pH, food changes...
Are made of smaller building blocks called amino acids. Pond fish require the same ten AA's as we do and make the rest. Our fishes "get" these amino acids in the form of small groups (peptides, di-, tri-...poly), break (catabolize) them down and re-build (anabolize) them into useful proteins.
Various diets of individual amino acids, peptides have been tried as "minimum media" to assess the roles of certain formulations and components. The same as for humans, these have thus far proven to be inferior than a mix of naturally-occurring foodstuffs.
Certain amino acids that must be provided exogenously, (from outside, the others being generated "endogenously"); Tryptophan, lysine and Threonine are their fancy scientific names, are mainly present/derived in suitably large concentrations from animal-source proteins. However beef and pork should not be utilized in pond fish foods. They contain too much unusable fat and have other undesirable characteristics. Many algae and other "vegetable" matter have a high protein count (concentration as a percent of dry weight) including these AA's. Other useful sources of proteins are white fish meal, crustaceans, worms, mollusks and insects.
Please note from the above: Plant proteins alone cannot provide sufficient amounts of essential AA's. It is not some raw number for the amount of protein present, but the components making up the protein and it's digestibility that are critical.
Coldwater (below 50-55 F) conditions warrant the use of 20-25 % protein concentrations in food. Warmer weather dictates the usefulness of protein ranges in the upper thirtieth percentiles. The difference in make-up is provided by carbohydrates from vegetable sources.
For those of you who are curious as to such high protein levels for benthic foraging fishes; don't be too surprised. The foods of these micro-phagous/detritivorous fishes are rich in protein sources: bacteria, interstitial organisms (meiofauna or aufwuchs), algae and invertebrates.
ii) Lipids: Fish Meals
To some large extent, for the sake of growth but not color, protein may be made up in foods in the way of fats. Carcass lipid levels for food carp have been recorded in excess of twenty percent. Sparing diets with more lipid though are dangerous. There is evidence of mortality, especially spring die-offs as a consequence of high fat build-up.
Carps have essential dietary requirements for certain poly-unsaturated fatty acids (PUFA's). These are best provided as fish oils. Fatty degeneration and fatty carcasses may be the result of insufficient PUFA, which should make up about 1% of the diet. Actual deficiencies are rare as supplemental feeds generally have excess oil content as do natural foods.
A note on fish meals. This is the single largest expense item in prepared foods. Fishmeal comes in two general formats "brown" and "white", mainly referring to source. Brown meals are typically produced from anchovy family (Engraulidae) and herring (Clupeidae) families, but also from rough or "junk" fish, all the fish being ground up into a fatty paste. White fish meal is prepared from fillets of hake, cod (Merluciidae, Gadiidae) and other families of fishes. It is far more costly. To my knowledge, only a few manufacturer's foods are produced with white fish meal domestically. The other's have more in common with Trout and Catfish feeds and are inferior. Brown fishmeal based foods are far more subject to spoilage and nutritional value loss. Smell them and you'll know.
In general carps use dietary proteins and lipids in preference to carbohydrates. Complex sugars seem to play a secondary role to protein and lipids as energy sources.
"The jury is still out" on the role of carbohydrates, particularly oligosaccharides in carp nutrition, especially fry.
Do you take them yourself? They are just as useful for your fish's nutrition, and similarly sufficiently available in otherwise complete diets. Over-dosing by using supplemented diets is virtually impossible. So where/when in doubt, add them through prepared foods or on your own. That's right I am implying, no, I'm saying outright that the water and fat-soluble vitamins you use are identical to those for fishes. Various mixing, baking and air-drying techniques are proposed for presenting as much of a physiological dose as possible.
There is a wide variety of vitamin deficiency symptoms (avitaminoses) that have been described (loss of appetite, poor growth, disorientation, pop-eye, color changes, skeletal deformities, hemorrhagia...). For fish having access to natural foods (the vast majority) avitaminoses are unlikely. The above symptoms are far more likely to result from stress, other nutritional deficiencies and disease.
v) Minerals, Trace Elements, Ash/Fiber:
Carps require the same dietary minerals (calcium, iron, magnesium and phosphorus) and trace elements (cobalt, iodine, zinc, copper, fluorine, manganese, molybdenum and sulfur) as "higher" vertebrates.
In earthen ponds there is very little chance of mineral deficiency. In prepared diets with a mineral pre-mix, none. Calcium and phosphorus are the most likely unavailable elements. Calcium is generally present in the water itself, phosphorus should be augmented. Most Japanese prepared feeds add monobasic calcium phosphate (@ 5%) to the mix.
Ash and fiber have their own technical and legal definitions. For our purposes they are benign, useless components.
iiiiii) Color-Enhancing Compounds:
Carotenoids and oxygenated carotenoids (xanthophylls), are oft touted as necessary or useful adjuncts to color production/ development retention or regeneration. These molecules are found spasmodically in different bacteria, fungi, vascular plants and are synthesized in novo in plants and some "plant-like" protists.
Most prepared foods attempt to introduce them into the stock from algal or invertebrate (e.g. shrimp, krill) bio-accumulated sources. Important notes: These compounds are water-soluble; therefore, however they are presented to your fishes, they must ingest and digest them readily. In a suitable environment, carotenoids are present from "natural" sources. This is to say, with a mix of micro-organisms, nutrient base, otherwise propitious chemical and physical pond conditions, your charges will receive some of these enhancing pigments. System cleanliness is not sterility.
These compounds are readily available and provided in feeds in corn gluten meal, paprika (yes, the spice), among others.
Yes, water is an essential nutrient for carps. The "cleaner" the better. See below under TDS, etc.
C. Co-Factors: General; Genetics and Developmental History:
Your fish are the sum-total of all their experiences...and their ongoing lives a juxtaposition of physical and chemical inputs to them and other life-forms and their reaction to same.
The known optimum growth temperature range for the species which is the common and ornamental carp (koi) is 23-30 C. At lower temperatures, growth falls off rapidly. At higher temp.s food seems to pass so quickly through the stock as to preclude any real growth/weight gain.
More important than any given temperature or range is its relative stability day to day. This is insured by the size and shape of the system, as large, deep and steep-sided as possible, it's location out of the elements, shading...
By and large, modifying the temperature "artificially" is expensive, dangerous and contraindicated.
2) Light: Quality, Strength, Duration, Periodicity:
As a function of interaction with nutrition as a variable, something in the way of regularity is stressed. Lights in the system are a very poor idea. Lights over the pond are fine (especially for attracting food insects) if used on a timer or just occasionally (once or twice a month).
3) pH, Acidity/Alkalinity:
pH's near neutral (7.0) are ideal with little a alkaline reserve. Once again, more importantly as a factor with nutrition is stability. Manipulating these aspects other than through proper filtration techniques and frequent partial water changes is not recommended.
4) Hardness, TDS:
Water with something less than one hundred parts per million total or carbonate hardness is preferable to the commonly encountered "liquid rock". Absolutely "soft" water is dangerous in terms of buffering capacity, but far easier to add to rather than subtract from.
Carps have an enormous capacity for adapting to a very wide range of conditions. Growth, color aspects are improvable through water quality engineering. You will have to decide which methods suit your desires/pocket book.
5) Other Possibilities:
An important consideration in carp nutrition is the activity of intestinal bacteria for aiding digestion and supplemental nutrients from ingested materials. Water chemistry, use of therapeutics, most anything that affects the system alters the presence and make-up of these alimentary populations. A regular, generally optimized environment is called for.
6) Water Movement:
Some purposeful circulation providing a resistant current for your livestock to frolic in and around presents (the same as for yourself) opportunities for generation of muscle tone and mass and elimination of excess calories.
7) Metabolite Build-up:
Probably the single largest factor after what you're feeding is consideration of doing away with or conversion of scatols, phenols, short-chain fatty acids and other "wastes" and by-products of your fishes metabolism's. Without their dilution and/or filtration or cycling out of the system, metabolites will stunt your fishes' growth and preclude the development of color and pattern.
Feeding good foods and paying the big cash for livestock without concern for metabolite build-up is a waste of money.
8) Stocking Density, "Dither" Fish:
Your feeding regimen will depend in part on stocking density. Be aware that unless you're rearing your specimens in a "vacuum" some natural feeding/nutrition is going on in addition to your "supplemental" activity. The more crowded your system is the more supplementation required.
I mention the use of (typically smaller) "dither" fish as a useful technique for keeping your system interesting and clean. I endorse this mix of smaller and larger specimens.
Most commercially prepared and home-made formulations call for a vast majority of the matter to be vegetable in origin.
Wheat, corn gluten meal, alfalfa and soybean meal are principally used. From stomach-gut content analysis (yuck) of wild stock diets consist of not much highly nutritious material: algae and algal-associated materials (aufwuchs), crustaceans, insects, worms, "mud". As stated this diet is very low in overall useful digestible nutrition. What can be assimilated is largely complex carbohydrates (like starches versus mono- & di- saccharides <sugars>), and proteins. Very little in the way of lipids (fats).
i) Fresh!? Rice, Algae, Cabbage...Frozen:
Fresh foods are best nutritionally and often for cost considerations; but are not as convenient as prepared foods. You will find a number of vegetal types: lettuce, cabbage, avocados (too much fat for use all the time), chard, okra, peas, spinach cited in the literature as useful, as well as many recipes for "mashes" with all manner of ingredients. My suggestions:
1) Be careful not to overfeed foods that will foul your system, whether they're consumed or not.
2) Rinse all and I mean all materials as they may well sport undesirable residues.
3) Resist cooking and baking foods excessively, if blending & air-drying (or even freeze-drying if you're wealthy) are possible/practical.
4) Rice is very commonly used in the orient as a primary or supplemental feed. It's cheap and nutritious and easy to use once you develop a regimen of preparation/storage/use. If you don't have a "rice cooker" yet, wake up and smell the ramen! Get one.
For very low stocking densities and extensive versus intensive aquaculture applications, planktonic algae are utilized as the main component for carp nutrition. Ponds are prepped and their physicochemical properties manipulated (pH, dissolved oxygen, carbonic acid content) to improve growing conditions for the important species of algae. (Bauer)
Making your own formulation is a combination of putting together the raw materials to satisfy nutrient requirements (protein, energy, essential amino acids and essential fatty acids) at lowest cost. Determining whether these presumed nutrients are available and biologically active is the trick.
ii) Prepared: Pelletized, moist,...:
Feedstuffs are processed (generally by milling) to increase their digestibility and pelletability. These processes also aid in inactivation of antinutritional factors growth inhibitors, toxins). Pellets make the feed much more water soluble/useable. Heat treatment is used in making feedstuffs to inhibit nutrition-losing factors and results in carbohydrates becoming more digestible.
Softer pellets are better nutritionally than harder, dryer ones. Their disadvantages are higher costs and shorter shelf storage life.
i) For Small Stock:
The nutrition of fry and young is not as well known as for adults, but obviously just as important. "Dwarfing" or making "Bonzai" koi is known from under and poor feeding at an early age. Commercial growers utilize algae cultures and finely divided cereal grain materials for starter foods. Some writers report specialty breeders utilizing rotifers and brine shrimp nauplii.
Commercially prepared and self-made "egg yolk" based fry foods, and pelletized and flake foods finely ground up have been used with moderate success. Careful, frequent small feedings are called for, coupled with modest water changes and adequate filtration.
Common carp hatchlings may resorb their yolk sacs in one day, reach 10-15 mg in five days and 50-60 mg within ten days. They are very good at capturing living and non-living food items, commonly consuming more than two times their body weight as postlarvae/fry.
As previously mentioned as larval foods, rotifers, brine shrimp to cladocerans (Daphnia, Moina, Bosmina) are often used, as well as prepared encapsulated egg formulae, for example Ewos C10 "Lavstart" from Sweden.
ii) For Adults
The less foods/feeding per season and more/less of protein and carbohydrate per temperatures are notable.
Females need a diet rich in animal source protein, vitamins and minerals for the development of egg cells in their ovaries. Males do not have the same requirement. Their protein content in supplemental feed may be reduced to about 15 to 20 %. Brood fish need to be conditioned by frequent feedings before and after spawning.
iii) Treatment/Prevention of Disease:
I've recently (FAMA 1/92) presented an overview of therapeutic use in foods. This is the single, best way to present physiological materials.
3) How Much/Often:
Just as for ourselves, too much of even good things is still too much. Too many calories in some notion of caloric balance is wasteful, leading to perhaps unwanted excess-growth-related changes (tapering of body shape, breaking of pattern, thinning/spreading of color) to passage and fouling of the system.
Pond fishes are "cold-blooded" and don't "fight the effects of gravity" as we do. They do not require near the same amount of useable food calories as ourselves per unit unit. A syncretized version of feeding lore in terms of how often to feed:
Below 45 F none (!) (food may be taken, not used)
46 to 55 F 2-3 times per week (more carbohydrate %)
55 to 60 F once per day
61 to 75 F twice per day
76 to 85 F once per day (more protein %)
above 86 F none (!) (maybe dangerous, not useable)
Depending on the make-up these foods, size and desired intent a few to several minutes time for ingestion is suggested per feeding. This often falls within a range of 3-5% of body weight per feeding. Excess food should never be evident.
As a general consideration, feeding much smaller amounts more frequently (continuously) is actually ideal. Observing carp, it is obvious they are more or less constantly searching/feeding.
5) Storage: Considerations and Suggestions:
Several techniques are employed intentionally to extend/ensure the useful shelf-life of foods; quick use after preparation, purchase in small quantities, FIFO (first in, first out) product rotation, packaging to reduce exposure to light and air, chemical/physical drying agents (desiccants), selective poisons (fungicides, bacteristatics...), extrusion/pelletizing technology...
Basically, foods do not improve with age (except for wines, vinegars, cognacs...). Lipids and proteins oxidize, losing nutritional and gustatory value. I suggest:
A) Buying as fresh as possible. Deal with a reputable source that in turn constantly updates it's shipments and date stamps.
B) Store your purchased food in the dark, in a cool area, away from bugs, rodents, dogs, children.
C) In it's original container! If you're mixing foods, mix them in the intended bag and store that maybe in a designated sealable container. Sterilize that container between replenishment of food stock. Keep the bag folded over and sealed closed, maybe with a "chip" bag clip, paper clips...
6) Purchase: Cost/Benefit, Perception of Value:
Good, prepared foods are expensive. Complete foods designed to be complete, that is, to require no other supplementation, natural or otherwise, contain a lot of expensive protein (mainly white fishmeal), sometimes shrimp, spirulina, vitamin and mineral premixes, costly packaging, transport... Are they necessary? Only if you're trying to optimize growth and color.
There is a great deal scientifically known regarding foods, feeding and nutrition of captive minnow-fishes. For the sophisticated and moneyed culturist a wide range of completely nutritious prepared foods fed in proper quantities in appropriate intervals, coupled with optimized/maximized water quality/environmental conditions will produce superior stock, color, conformation and pattern-wise given initial genetic endowment , propitious developmental history and lack of deleterious bouts with infectious and/or parasitic disease.
For the mere mortal, securing decent specimens at reasonable cost and not going flat broke incurring the related costs of the obsession/passion of koi keeping, including food costs is about all they are shooting for. Towards this ends, a working knowledge of what, how often, why, how much of foods and feeding includes a consideration/appreciation of all the above; and action in terms of adequate nutrition within guidelines of their desired effects versus time, money and general resource constraints.
Bauer, K., 1983. Algae in carp culture. Fischwirt.; vol. 33, no.11
Chow, K.W., 1982. India. Carp nutrition research at the Freshwater Aquaculture Research and Training Centre, Dhauli: Establishment of a nutrition laboratory and initiation of a diet development programme for carp polyculture. A report prepared for the Intensification of Freshwater Fish Culture and Training Project. FAO; Rome (Italy)
Fenner, R., 1992. Furunculosis, Hole in the Side Disease. FAMA 2/92.
Michaels, V.K., 1988. Carp Farming. Fishing New Books; Farnham (U.K.)
Renukaradhya, K.M. & T.J. Varghese, 1987. Formulation, processing, and water solubility of pelleted feeds with varying levels of protein used in carp nutrition studies. Fish. Technol. Soc. Fish. Technol., Cochin.; vol. 24, no. 2
Ruckle, Duane. Nutrition For Koi. AKCA V.2 compilation
Saleh, K.I., 1984. Research on carp nutrition (Cyprinus carpio L.). Laboratoire D'Ichthyolgie Appliquee, Toulouse (France)