Fish Biology 
by J. Charles Delbeek M.Sc.

Fish Nutrition: A Vitamin a Day Keeps What Away?
The majority of research on the nutritional requirements of fish has,
not surprisingly, been performed mainly on commercially important
fish such as trout and salmon. However, much of this information can
be extrapolated to marine tropicals since fish have basically the
same muscle and organ systems be they Rainbow Trout or Emperator
Angelfish; they all use the same metabolic pathways (Fruland and
Miller 1980). This research has shown that there are four main
constituents in the diets of fish, proteins (chains of amino acids),
carbohydrates, lipids (fats) and vitamins, which are important for
both growth (anabolism) and as an energy source (catabolism) (Moyle
and Cech 1982).

Proteins are composed of amino acids, so far the following amino
acids have been shown to be essential for fish, arginine, histidine,
isoleucine, leucine, lysine, methionine, phenylalanine, threonine,
tryptophan and valine (Moyle and Cech 1982). The only problem is that
the amount of each type required varies from species and excessive
amounts can be detrimental to a fishes health (Moyle and Cech 1982).
Missing amino acids can result in scoliosis (curvature of the spine)
in fish (Moyle and Cech 1982). Proteins are very important in the
growth of fish and research has shown that if certain proteins are
lacking, then growth will be stunted. In the wild, omnivorous fish
normally feed on abundant live organisms, rich in proteins which
provide a valuable energy source (Moyle and Cech 1982). However, many
commercial foods lack abundant protein since it is expensive and the
fish use a lot of energy to break down large, complex proteins. As a
result, carbohydrates and lipids are substituted as energy sources
(Moyle and Cech 1982).

Carbohydrates are found primarily in plants and carnivorous fish have
problems digesting it. Lipids, on the other hand, are found in both
plant and animal tissues and are completely digestible (Moyle and
Cech 1982). Many herbivorous  fish have symbiotic bacteria in their
guts which digest the carbohydrates and liberate its energy to the
fish. Lipids provide much more energy than do carbohydrates and they
also supply fatty acids which are used for the construction of energy
reserves in fish. Predaceous fish normally have very high growth
rates due to their diet of live fish, which are naturally high in
lipids (Moyle and Cech 1982). The importance of protein and lipids as
energy sources, becomes quite apparent during periods of starvation.
The quantities of both proteins and lipids are significantly reduced
in straved fish (Moyle and Cech 1982).

In any animal, the metabolic conversions which occur during digestion
usually require the presence of cofactors to proceed (Moyle and Cech
1982). In may most cases vitamins are these cofactors. Vitamins are
an important nutritional group which many hobbyists fail to provide
for their fish. In the wild, fish and invertebrates feed on varied
diets of fresh food which supply all of their vitamin requirements,
however, in the home aquarium, the hobbyist usually provides only a
monotonous diet of one or two dried foods supplemented with some
frozen foods, which may not meet these needs (Fruland and Miller
1980). Table 1 lists the vitamins known to be used by fish, how they
are used and the symptoms associated with a deficiency in that
particular vitamin. However, I would not recommend that you use this
as your only diagnostic tool for the simple reason that there are a
number of factors which will produce similar symptoms (i.e. poor
water quality can produce rapid breathing and skin lesions, a protein
deficiency can cause poor growth, and bacterial infections can
produce a multitude of symptoms). The marine aquarist should,
however, be aware that a failure to provide a balanced, varied diet
can lead to vitamin deficiency problems. Symptoms of a vitamin
deficiency do not happen over-night, it is a slow, gradual process
which depends on the time required for the critical level to fall
below the body reserves of the fish (Fruland and Miller 1980).
Similarily, simply providing the deficient vitamin will not result in
an immediate recovery, this will only occur over a period of time.

Now that we have explored some of the factors involved in proper fish
nutrition its time to get practical! What can be done to ensure that
our fish are receiving the proper amounts of protein, carbohydrates,
lipids and vitamins? The first and most logical solution is to feed
them their natural foods. For many of us this is not practical,
however, with the increased popularity of "live rock" in marine
aquariums many of the smaller, crustacean eating fish species can be
provided with a renewable live food source. The "live rock" brings
with it many microscopic crustaceans that many fish relish. If the
tank it setup without fish for a few months, these animals are given
the chance to multiply to such an extent that when a few fish are
added, the food animals can reproduce at a pace to keep up with the
rate of predation. Of course, this is a delicate balance and the
sudden addition of too many fish can cause irreversible damage. For
herbivorous fish, live plants such as the macroalgaes (i.e. Caulerpa)
can provide a natural food source. In the case of other fish, such as
butterflys and large angelfish species, the situation is trickier.
Some species have dietary requirements that we cannot possibly
duplicate in the aquarium at present, I am thinking of the sponge
eating angels and coral polyp eating butterflies. For the others a
diet, rich in variety is called for. To ensure that the full range of
vitamins are present, vitamin supplements can be added to dried and
frozen foods before being fed to the fish. One excellent method is
the use of a homemade food preparation as outlined in Atoll vol.1
no.4, to which you can add vitamin supplements. I have used Dick
Boyd's VitaChem with some success, by soaking freeze-dried brine
shrimp, Tubifex and Hakari Turbellina in a small container of the
solution before feeding it to my fish. A third possibilityis to add
the vitamins directly to the water. As previously mentioned in this
column (Atoll vol.1 no.3) marine fish actually drink water, therefore
any vitamins in the water would be absorbed by the intestine. The
are, however, problems with this method. First of all you would need
to add a greater volume of vitamin solution to the tank to reach the
concentrations that would need to equal that found in vitamin
enriched foods. Secondly, if you are using U.V., ozone, activated
carbon or protein skimmers the vitamins will quickly be removed or
destroyed before the fish can get the full benefits of them. Also,
adding vitamins directly to the water will increase the organic load,
resulting in an increase in nitrogenous wastes (ammonia etc.).
Thirdly, vitamins are rapidly lost in the aquarium due to the
alkaline conditions of the water, light, oxidizing agents and use by
other oragisms such as bacteria and algae (Fruland and Miller 1980).
Many vitamins are not very stable and have a limited shelf life,
therefore, if you use a commercial vitamin solution check the expiry
date. I feel that if a manufacturer does not put on such a date (this
applies to test kits too!) that they have limited knowledge or lack
of concern for the hobbyist. Most vitamin solutions designed for
human consumption have such dates stamped on their labels. Baby
vitamin solutions generally contain all the necessary vitamins fish
require and I have used them without any detrimental effects.

Make the addition of vitamins a routine part of your feeding schedule
and you will ensure that your pets will live longer and healthier
lives. Remember a vitamin a day keeps .....


Table 1. Vitamin function and symptoms of deficiency.

Water Soluble Vitamins
Thiamine (B1)

   Functions: - aids growth, digestion and fertility, nervous system
Deficiencies: - poor appetite, muscle atrophy, convulsions, loss of
                equilibrium and poor growth

Riboflavin (B2)

   Functions: - vision, protein metabolism and enzyme functioning
Deficiencies: - photophobia, cloudy lens, dim vision, abnormal
                colouration of the iris, striated constrictions on the
                abdominal wall, dark pigmentation, poor appetite,
                anemia and poor growth

Nicotinic Acid (niacin, B3)

   Functions: - plays an important role in lipid, protein and amino
                acid metabolism
Deficiencies: - loss of appetite, poor growth, lesions in colon,
                erratic motion and weakness, edema of stomcah and
                colon

Pantothenic Acid (B5)

   Functions: - adrenal functioning, cholersterol production, normal
                physiology and metabolism
Deficiencies: - poor growth, sluggishness, clubbed gills, loss of
                appetite, hemmorhagic skin and cellular atrophy

Pyroxidine (B6)

   Functions: - plays a vital role in enzyme systems and protein
                metabolism
Deficiencies: - nervous dissorders, fits, loss of appetite, poor
                growth, rapid and gasping breathing, flexing of
                opercles and hyperirritability

Cyanocobalamin (B12)

   Functions: - enzyme systems, cholesterol metabolism
Deficiencies: - poor appetite, poor growth, anemia and dark
                pigmentation

Ascorbic Acid (C)

   Functions: - enzyme systems, bone, tooth and cartilage formation
                and healing
Deficiencies: - hemorrhagic shin, kidneys, liver, intestine and muscle
                tissue, eye lesions and scoliosis of the spine

Biotin (H)

   Functions: - enzyme systems, purine and lipid synthesis, oxidation
                of lipids and carbohydrates
Deficiencies: - loss of appetite, poor growth, anemia, skin lesions
                and muscle atrophy

Choline

   Functions: - good growth and food conversion
Deficiencies: - poor growth, poor food conversion, hemorrhagic kidney
                and intestine

Folic Acid (M)

   Functions: - blood cell formation, blood glucose regulation and
                fish metabolism
Deficiencies: - poor growth, lethargy, dark skin, anemia and fragility
                of the caudal fin

Inositol

   Functions: - cell membrane permeability
Deficiencies: - poor growth, distended stomach, skin lesions and
                increased gastric emptying time

p-Aminobenzoic Acid

   Functions: - unknown
Deficiencies: - no abnormal indication in growth, appetite and
                mortality


Fat Soluble Vitamins
Vitamin A

   Functions: - normal vision, cell growth and resistance to infection
Deficiencies: - poor growth, poor vision, abnormal bone formation and
                hemorrhaging at the base of the fins

Vitamin D

   Functions: - calcium blood levels (?)
Deficiencies: - unknown

Vitamin E

   Functions: - antioxidant, may paly a role in muscle cell
                respiration
Deficiencies: - anemia and poor growth
 
Sources: from Fruland and Miller 1980; Moyle and Cech 1982


References
Fruland, R. and W. Miller 1980. Vitamins and the marine aquarium.
FAMA 3(5): 36-75.

Moyle, P.B. and J.J. Cech Jr. 1982. Fishes: An Introduction to
Ichthyology. Prentice-Hall, Inc., New Jersey.