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A. Overview of Aquatic Life Nutrition
iii. Freeze & otherwise Dried
iiii. Vegetable & Algal
B. Some Conclusion
A. Overview: Captive aquatic animals in the way of fishes and most invertebrates have remarkably similar nutritional requirements as ourselves. At the atomic and molecular levels the same few fats and carbohydrates, ten (maybe eleven) amino acids (the "building blocks" of proteins), vitamins, minerals, "trace elements", and water. The same as humans, most can make other necessary materials (e.g. other amino acids) and must derive from outside sources (exogenously) others (e.g. vitamin C). Also, like "po" folk, if they are offered too much of the "right" and/or "wrong" things, there is the possibility of lack of or mal- nutrition, poor developmental histories, nutritional disease (deviation from a "normal" or healthy state) and enhanced susceptibility to other co-stress factors.
Basically, our job as aquarists in the way of nutrition is the appropriate presentation of a suitable mix of food items, in an adequate format at a workable interval of enough of what it takes biochemically to make our stock do what we want it to do (e.g. reproduce, grow, color up...). Just like your own nutrition, too much deviation from the way it's s'posed to be results in undesirable attributes; irritability, poor health, sterility, death and the like.
One can be endlessly bothered by the minutiae of what accounts for "fish nutrition" articles, even books. These pour and bore on endlessly as to "the function" of one bio-active substance after another; with little enlightenment as to what a mere mortal without a PhD and lab might/should/must do. This short piece is intended to offer some (all that's needed?) background and quiet the nerves of the earnest pet-fish type foods & feeding wise.
1. Natural Foods:
One of my favorite misused/misuseable nouns and adverbs. What is "natural" versus not or un-natural? Is vitamin C extracted from rose hips any different or better than vitamin C from other sources? Of course (!) not. The molecule is the same, identical, exact; with the same "activity", essence, "aura", bio-chemical consequence. My advice, buy the quantity at the best price and forget about "the source".
If by natural, live is implied, allow me to present my opinions pro and con: First of all the negative:
1) Live foods are relatively more expensive per unit nutrition, due to the vagaries and costs associated with capture, transport, maintenance and service. Is serving you a live/right-then-freshly-killed chicken more nutritious than one that has been commercially "dressed"/prepared? Why not? Think!2) Live foods pose more of the possibility (than other formats) of introduction of pests, parasites, infectious disease and pollutants. As per human foodstuffs, of the known toxicants, the most virulent are "naturally" occurring (like botulism).
Obviously, there are techniques for minimizing these risks; using marine foodstuffs for freshwater and vice versa, rinsing before use... And once again, these add directly to cost.
3) Live foods are inconvenient. How many marriages have been rocked by live worms, feeders, crickets et al.? More than I would care to admit, being in the industry.
4) Live foods incite and intensify "predacious" behavior in a system. Though I am not readily able to cite a scientific source for this, feeding live foods makes animals "meaner" (more antagonistic for you ethologist types). I could drone on with numerous anecdotal evidence of same, but for now I'll spare you.
& now the "pro" argument:
1) It's more "natural" for my charges to be infected, my systems to be infested, my fishes and invert.s to be aggressive.
2) I enjoy spending my money and days at the aquatics stores buying feeders, worms... Or culturing same.
3) For folks who lack a sense of self-importance (power?); other than driving like knuckleheads, this gives them that certain sense of satisfaction.
4) Lastly, and perhaps my only valid argument for live foods; some "varieties" of livestock do poorly (or not at all) in captivity without their meals live and kicking. Most all these species may be trained to accept prepared foods, others should not be kept. Your conscience will be your guide, along with your pocket book.
The flat out "truth" of the matter is the livestock we keep in artificial systems are for the most part "man-made" and would do "better" nutritionally fed a "prepared" diet. It's cheaper, safer, more nutritious, more convenient... For the same reasons we feed ourselves and our companion animals (doggies and kitties) pre-prepared foods. There is nothing wrong with them! So, let's get on with this story:
2. Prepared: foods of all types of formats; frozen, dried in a few ways, pelletized in even more...are/can be completely (this is a scientific term) nutritious.
i. Flake/Pelletized: are amongst the most popular formats. These foods are readily accepted by most species maintained, easy to store and use, less-fouling (never not; let's be honest), "harder" to over-feed, and do the job in all ways food wise. They come in softer to harder, crumbly to crusty, flatter and fatter, colorful and not ways.
A few words concerning "freshness" as a function of palatability and nutritiousness. The legitimate manufacturers (e.g. Tetra, Sera, Aquarian, O.S.I. et al.) go to amazing lengths to compose, prepare, package and other ways assure the quality of their products. Do not thwart their efforts! Buy what you can use in a few weeks to a few months and store it as they suggest. Don't be stupid! Don't waste your time/money/fish's health on "re-packaged", "bulk", or "refills". How many times do I have to re-state the reasons? Would you eat nothing but a box of breakfast cereal that purports to be "wholesome" & "completely nutritious" that had been sitting around, exposed to the air, light, bugs, etc. for who knows how long? Check it out, I've been there: Commercially prepared foods are packed with "shaker" mechanisms and often in a "high" nitrogen environment to prevent oxidation of nutrients (mainly fats and proteins) through exposure to the atmosphere. Just spill out the contents of a new canister. Smell it; try to get it all to fit back in the can. It's packed in this way for good reasons. Don't buy "re-packaged" fish food and tell me you're an aquarist; you're a fish killer! Okay; hey thanks for letting me get that off my chest.
ii. Frozen foods are great! Though perhaps not as convenient as dried, they are available in a myriad of types, sizes and formats, appear more palatable to some stock, and are bargains compared to strictly "fresh" foods. If/where processed properly, frozen foods are just as nutritious as fresh.
Cubes, "packs" of single species (e.g. Brine shrimp, krill) or blends (like Discus "mixes", Ocean Nutrition's "Angel Formula") are the present epitome of attempts at complete nutrition in an appealing format to aquatics and their owners.
Some writers advocate defrosting before introducing into the system, some even rinsing; I have yet to experience/observe ill effects from just "sticking it in". For ease of dissemination and perhaps avoiding a cold tummy ache, frozen foods might be better off broken up through setting in a container and squirted or poured in.
iii. "Dried" foods through air, sun, lyopholization ("freeze-drying"), are an appropriate means to the ends of getting nutritives to your organisms in a "pretty" format except for one consideration: they are inordinately expensive for what you're getting. Check out the equivalent price per ounce, let alone pound. You will be shocked. If you have a freezer available (!?) you'd be better off fiscally using frozen.
Some argument can be made for viable food value loss...but the economics should be enough to convince most folks that this method is generally more expensive than the trouble of other formats use will warrant.
iiii. "Green Foods"; semi-fresh, dried, flake, pelletized or otherwise are sometimes touted as necessary/recommended for certain species. Most have little nutritional value (some vitamin and mineral content may be delivered in this manner), but do render "roughage" and "give the critters something to do". One of my optimal sources is the dried algae (noritake, kombu among others) available through the "oriental" food sections/outlets. Canned, cooked okra, zucchini and the like are fine except for the build up of oxalic acid (in the long haul). Lettuce of different types and other green-leafys are probably best considered "filler". "Fortified" prepared green foods in the trade are good only for the fortification and fiber/ash content.
My favorite advice as usual; grow your own. Do have some plant material, algae... available for the occasional, casual munch by your stock. This technique yields many benefits; amelioration of the environment, reduction of aggression, reduction of metabolites...
II. Feeding: Over the range of species, sizes, even individual variation in such large groups of organisms it may seem hard to make useful generalizations; but here goes. Know your livestock and system. What do they eat, have they been eating? What are the consequences of varying temperature, lighting, other aspects of water quality on their desire to ingest, ability to digest, utilize and egest (excrete through gills, urine, feces) any of the given/offered foodstuffs? For instance, yes it turns out that more frequent feeding of higher (concentration) protein foods in greater total quantity does shorten the life span of carp (Cyprinus carpio)
the species also called Nishikigoi (koi). Is the enhanced growth, color, whatever you're shooting for worth this trade-off?
Feed more frequently, smaller amounts is good safe advice; never to where food lays about and rots. Occasionally "stuffing" or starving your livestock is not really a problem. As you might guess, this is probably a situation they run into in "the wild".
My last pitch about over-versus-under feeding, underfeed. When you go on vacation (what's that?) hide your foods! Throwing them away would be better, all incidents considered, than entrusting insolent youth or worthy neighbors. Unless you're gone for months, and in some cases, even if you are gone for months, you and your livestock would be better off nibbling on the plants, gravel, each other then counting on other's not to over/mis-feed.
Some (electrical, mechanical) automatic feeders are to be lauded, the "in-the 'tank blocks" are at best a feeding placebo and at worst a melting chalk buffer-gravel clogger. Try putting one in your mouth! Yuck!
B. Some Conclusion: Well, I did promise something of one:
What is nutrition? The ready assimilation of a mix of blah blah blah. How much is enough, how often, how?
Just what is meant by "protein content". Proteins are made up of smaller building blocks called amino acids, which in turn denote specific arrangements of carbon and hydrogen skeletons, an amino group (nitrogen and hydrogen), a carboxylic acid group (COOH), and in two types, sulfur. Some sources of amino acids are more "animal" abundant (tryptophan, lyseine, threonine) and therefore more "expensive" as a function of food "web", "pyramid" efficiency. So simple protein content without some description of source or amino-acid mix is ludicrous.
What about caloric counts? Calories are a measure of "heat content", the capacity to raise the temperature...through oxidation (burning, if you will). What does this have to do with nutrition? Gasoline for internal combustion engines has lots of caloric value. Don't try feeding it to yourself or your fish.
Become a conscientious consumer. Pay for what you're buying! All foods are not alike. As an example, only two domestically
produced "koi" foods are made with "white" fish meal; all others with "dark" fish meal oily fish like anchoveta (Engraulicypris mysticetus,) "ground fish", "rough fish" (substitute trash fish), sharks of various types...). One of the "good" manufacturers/brands is Star Milling's Ace Hi line. To reduce my liability to suit I'll leave it up to you to research what you're feeding.
Ho boy. Let's see; oh yes: Along with genetic potential, developmental history, chemical/physical/social suitability of the environment, presence and degree of infectiousness of disease-causing organisms, foods and feeding rank right up there as determinants of your livestocks vitality. Know what you're doing nutritionally and...do it!
Blasiola, George. 1983 Maintaining Good Fish Health Through Proper Nutrition. FAMA March 1983.