The text and photographs for this web page are all from the
magazine
Organic Gardening and
Farming; November, 1973
For details on the availability and price of catfish fry or
fingerlings in your area,
please contact your county &/or state agricultural agent. Another good
source
for such information is any local state or community college that happens
to
have an aquiculture course within it's curriculum.
Philip Mahan demonstrates how a fish is transferred from
the fry tank to the barrel.
RAISING CATFISH IN A BARREL
A biological food chain in the back yard produces fresh fish
for the table and compost for the garden.
By Philip and Joyce Mahan
After some study and experimentation, we have set up a productive
food chain-- table scraps to earthworms to catfish--in our back yard. The
project is satisfactory in many respects, utilizing waste materials to produce
fresh fish for food and at the same time yielding ample compost for a small
garden. The material cost is minimal. The whole operation can be set up for
less that $15.00. The equipment occupies only about 12 square feet of space,
and the entire assembly can be easily moved if necessary.
The materials can be very simple: Two 55-gallon steel drums, three panes
of glass 24 inches square, and a medium-sized aquarium air pump. One of the
drums will serve as a tank for the fish, oxygen being supplied by the air
pump; and the second drum should be cut in half to provide two bins for the
worms. The panes of glass are used as covers for the worm bins and fish tank,
and for ease and safety in handling can be framed with scrap lumber.
We chose catfish because they are readily available in our part of Alabama,
and reach eating size in a summer. Various small members of the sunfish family,
such as bluegill or bream, would also be suitable.
While we readily admit that our plan has no commercial possibilities, we
know that we can produce, for our own table, tasty fresh fish that is
uncontaminated and costs practically nothing, both considerations being highly
relevant at this time.
Fish are usually efficient food producers; a one-pound fish yields approximately
10 ounces of food. Further efficiency is indicated by the fact that fish
fed on commercial fish ration convert about 85 percent of their food to meat.
While we are not prepared to compute the technical data about food conversion
in fish on an earthworm diet, we can readily state that the fish relish
earthworms, and do grow well on this food.
Spraying the water back into the tank aerates the water and at the same tie
releases the ammonia produced by excretory matter in the water. Because the
oxygen requirements of fish are quite high, the faster the circulation of
the water, the faster the growth of the fish.
We decided to keep our equipment as simple and inexpensive as possible at
the beginning, but to use the maximum stocking density advised, keeping 40
fish in a 55-gallon drum. Although inexpensive circulation pumps are available,
we chose to use a METAFRAME HUSH II aquarium bubbler for oxygenation and
a garden hose to siphon off water from the bottom of the barrel.
We take off 15 gallons of water per day, but as we run the waste water onto
the worm beds and adjacent garden, the cost is negligible. Although we have
creek water close at hand, we were advised to use city water to avoid the
introduction of undesirable algae and fungi that might be harmful to the
fish. Because city water is usually quite highly chlorinated, it is necessary
to draw the water in 5-gallon buckets and let it stand for a day in the sun
before emptying it into the drum to replace the water siphoned off. We have
seen no evidence of oxygen starvation in the fish with this method of water
circulation.
The most important variable we have found is water temperature. Catfish will
feed at temperatures as low as 40 or 45 degrees, but their greatest growth
is achieved at 84 degrees. We noticed a decided increase in feeding activity
when we painted the barrel black and moved it into full sun. Leaving the
buckets of water in the sun not only speeds chlorine dissipation, but warms
the water as well. In areas where city water temperatures are close to the
growth optimum, the chlorine can be removed by setting the hose nozzle at
fine spray, and the barrel can then be filled directly from the water supply.
Although summer growth is greatest, the project continues throughout the
year. By judicious use of sun when possible, plus auxiliary heat when necessary,
winter growth can be kept at a fairly high level.
When water temperatures are right, the fish will feed so enthusiastically
that they may leap completely out of the barrel. For this reason the top
of the barrel should be covered completely with a pane of glass which will
also help in keeping the water warm. Because fish feed most eagerly in late
evening and early morning, we feed them at these times of the day. As with
earthworms, care must be taken not to overfeed. In warm water and bright
sunlight, any uneaten worms will die and decompose rapidly, giving off gases
which are poisonous to the fish.
Transferring any grown animal to a confining environment produces the equivalent
of cultural shock, and is followed by a period when feeding is light and
growth is slow. At this time special care must be taken not to overfeed.
Unless fish can be found that have been hatched and grown in a tank, small
fish should be selected to stock the barrel, as their adaptation time is
proportionally shorter that that of larger fish. To eliminate as much
transplanting shock as possible, we use a large wooden box, lined with two
layers of polyethylene sheeting and covered with an old door, to stock with
fry. By the time the fry reach fingerling size, they can be transferred to
the barrel as replacements are needed, and very little shock is evident.
An insect lamp over an opening in the cover of the fry tank permits the small
fish to eat at night while ridding the garden of night-flying pests.
Earthworms, as any angler knows, are food for fish in their natural habitat;
and most fish in captivity prefer live food to the dehydrated type. Kitchen
scraps make excellent food for earthworms, and even the most careful organizer
will have enough refuse to feed, quite handsomely, 5,000 to 10,000 worms.
We found that growing earthworms at home is not difficult. The basic materials
are easily arranged, and the earthworms' demands are simple. All they require
are a protective container, reasonable temperature control, adequate moisture,
not too much food, and a light loose bedding which is never allowed to become
acid.
The steel half drums are ideal worm bins as they are effective
protection against the earthworms' predators in addition to being quite
inexpensive. They have the added advantage of being movable so that as cold
weather approaches, the worms can be carried to an enclosed porch or basement
to continue composting activity and fish food production throughout the
winter.
Each half-drum will house between 4,000 and 6,000 worms. The two half-drums
are utilized most effectively if they are alternated so that the worm population
is allowed to build up in one, while the second supplies the fish food. The
eggs that remain after the worms are removed will serve to start a new supply
when the first drum is converted to feeding.
Worms will start breeding when they are about 90 days old. Each worm, possessing
reproductive organs of both sexes, will produce an egg capsule per week,
containing from three to 25 eggs apiece. The most economical way to establish
worm bins for a home food-chain and composting operation is to begin with
capsules. Although a little more time is required initially, there will
ultimately be more worms available to work with. Under the protected conditions
of a worm bin, the survival rate of young worms is very high.
The type of worm selected is not important. There are two compost-bait types
raised commercially -- usually known as "brown-nosed worms" and "red wrigglers."
Either type may be purchased from most dealers.
The bedding for the worm bins may be any organic material that is water-absorbent
and does not pack so as to exclude oxygen and impede the worms' movement.
Leaves and old straw are good, as is aged sawdust soaked in several waters
for a week or so. Ground peat moss, being odorless, is ideal if the worms
are to be kept inside. Soil should never be used as it contains no nutriment
and is likely to pack.
It is safe to assume that earthworms can eat any kitchen scraps except citrus
rings, vinegar dressings, and bones. Though they eat almost anything given
them, their intake of food, and likewise the production of compost, can be
increased by frequently feeding foods that are especially tasty to them.
The prime consideration is to avoid overfeeding. Although worms thrive on
decaying food, they should never be given more than they can consume in 24
hours.
The dangers of acidity cannot be overemphasized. It is the only real hazard
in worm raising. Acid bedding frequently destroys an entire worm farm in
a few weeks. To maintain accurate control over the acidity, one should use
a soil test kit or a pH test strip of the type used by industrial and medical
laboratories. Tests should be made at least once a week, and the pH factor
(degree of acidity) should remain between 5.5 and 6.5 on the scale. A reading
of 5.0 or below means danger, and immediate steps must be taken to neutralize
the bedding with an application of pure ground agricultural limestone.
It is important to read the label carefully to verify that the limestone
does not contain any added phosphates which also bring disaster to a worm
bed.
The drums should be located in an area protected from temperature extremes.
Optimum temperatures for feeding and growth are between 60 and 70 degrees,
but worms will thrive in most summer climates if the beds are well shaded
and the bedding is kept loose. During the summer months, the bedding must
be sprinkled daily, but it should never grow soggy. The glass tops on the
half drums serve to conserve moisture, but they will not prevent crawling.
Worms have a tendency to roam at night during damp or rainy weather unless
preventive measures are taken. A small light over the bed is an effective
deterrent to their wanderings, while an equally effective measure is to cut
a remnant of carpet to fit the drum exactly and lay this on top of the
bedding.
The table scrap-earthworm-catfish food chain, even from its inception, was
never intended to evolve into a money-making project. It was simply an effort
toward a better way of life through cooperation with the forces of nature;
and in this respect, our project has been a complete success in more than
one way.
First of all, we have a regular supply of fresh fish at minimal cost. A
seven-ounce catfish fingerling grows to 25 ounces in a summer, thus producing
a pound of food in four months. In the second place, we have netted ample
compost for our vegetable garden, thereby further insuring a low-cost and
nutritive food supply. In addition, and perhaps this is the greatest benefit
of all, we have the satisfaction of working with growing things and the
gratification of knowing that we have not wasted the earth's resources. We
have made an elementary biologic principle work in our own back yard.
IF YOU'RE THINKING OF RAISING CATFISH
EDITORIAL NOTE: Because we believe many of our readers will want to raise
catfish on their homesteads, we referred this article to Dr. William O. McLarney,
of the New Alchemy Institute, Woods Hole, Massachusetts, for review. The
questions he raised were then referred to authors Philip and Joyce Mahan,
whose replies appear below.
The fist were channel catfish.
Our fish were not fed exclusively on earthworms in that we started them on
commercial catfish food. Because it is very difficult to teach pond-grown
fish to eat in confinement, we offered them exactly the same food they had
been eating in the pond. We continued these rations for about four weeks
before their response was sufficiently enthusiastic to risk changing food.
Then the earthworms were introduced gradually -- a few at a time -- until
the fish accepted them. Some of the fish recognized the worms as food
immediately, and within a week the water literally boiled when the worms
were thrown in. We wondered, then, if they might not have started eating
more readily if we had used the worms initially.
Weight of fish: We don't have any figures at all on the weight of the fish
we started with, and we didn't weigh any before we ate them. As we stated
in the article, we began with 40 fish -- fingerling size. Although we arrived
at this number on the basis of Auburn's ratio of water as estimated by the
fish farmer from whom we got the fingerlings. He didn't weigh the fish and
we don't remember what that estimated weight was. We didn't know this thing
was going to work.
Earthworms: Again we have no figures on pounds of worms used. For reasons
of ethics (we advertise in OGF), we didn't mention in the article that we
are in the worm business. Since we have so many worms around, it just didn't
occur to us to keep records of how many we used. We simply tossed the worms
into the barrel until the fish stopped eating. We fed once a day, but we
don't think that all of the fish ate at every feeding. I would estimate an
average of 75-100 worms per day. The worms were small, not weighing more
than an ounce per hundred. We were careful not to feed breeders to the
fish.
Table scraps: We have been feeding table scraps to earthworms for a number
of years; and to date, we have not weighed a single scrap. We can, however,
offer fairly precise figures on this step. Earthworms are reputed to produce
their own weight in compost daily; but our experience has not indicated that
they really do. A thousand worms weigh 13 or 14 ounces, but daily feeding
per thousand does not approach that weight. We usually keep a container of
around 2,000 composting worms in the kitchen, and I give them a couple of
table spoons of selected (that is to say, soft and mushy) scraps each day.
In liquid measure this amount would be only two ounces.
It never occurred to us that a nutritional deficiency might develop in fish
fed only on earthworms. I doubt that either of us would have recognized
malnutrition if it had occurred. As we don't have backgrounds in biochemistry,
we are not in a position to make any statements concerning the nutritive
value, qualitative or quantitative, of earthworms. We did definitely notice
a considerable increase in feeding activity when we started giving worms.
In fact, we ate our first fish -- seven of them -- when they were only ten
inches long because they jumped out of the barrel, and we didn't want to
put them back for fear they had been injured. We feed our tropical fish (Red
Oscars) earthworms also, but we can't continue the diet for more than two
months at a time because the fish get so lively and eager for food that they
leap out of the aquarium whenever we lift the cover for feeding. I would
say we are inclined to agree that earthworms are a near-perfect fish food.
