It’s becoming increasingly evident that we’re going to run out of
sustainable fish stocks in the years ahead—is aquaponics really a viable
solution?
The world is always changing around us and the face of agriculture
and food production is changing as well. A constantly increasing world
population means more urban sprawl is taking over what was once fertile
farm land—how are we going to manage to grow enough food to keep up with
our ever-growing numbers, especially the millions who live in
drought-stricken, arid climates? Fish numbers are also dropping
throughout the world’s oceans, leading experts to predict increasingly
severe global shortages.
How about aquaponics? Aquaponics is an ingenious growing system that
merges edible fish production with hydroponics. In aquaponics an
artificial ecosystem is created in which fish are fed, their waste is
broken down into more absorbable forms by beneficial bacteria and the
converted waste is then pumped through the system, where it feeds the
plants. The plants act as a natural filter, cleaning the water—which is
then recirculated through the system. Aquaponics is looking more and
more like it’s going to be one of the best solutions for future
generations seeking sustainable ways to produce healthy organic food.
Making aquaponics work
Aquaponics is a blending
of two important ideas, combining fish farming with hydroponics
(soilless gardening). Edible fish that do well in closed environments
are required—tilapia, white bass, crappie and barramundi are species
that are used in many commercial and home aquaponic systems. These fish
will feed and their urine and feces will be a waste product. In normal
fish tanks or fish farming systems the waste builds up and makes the
water toxic to the fish—the waste-filled water then needs to be purified
and would normally be either filtered or disposed of.
In aquaponic systems this is not the case, however—the fish waste
actually makes great plant food. The waste-filled water is recirculated
throughout the system instead of being flushed away. One very important
aspect of aquaponics that needs to be understood is that it is not just a
symbiotic relationship between fish and plants—there is another system
of organisms operating within every aquaponic system that is crucial to
success. This is the network of beneficial bacteria that needs to exist
in every aquaponic set-up. The beneficial bacteria nitrosamonas
spconverts ammonia from fish urine and feces into nitrite and the
beneficial bacteria nitrobacter sp then converts the nitrite into
nitrate—a form of nitrogen that plants can absorb and fish can tolerate
in their water at low levels. Without the action of this network of
beneficial bacteria the water would develop toxic levels of nitrite
(even small amounts are toxic) and both the fish and plants would
eventually die.
This network of beneficial bacteria is fragile and must be cared for
as carefully as your fish or plants. This means that you can’t use any
chemicals—including hydrogen peroxide or pesticides (chemical or
organic)—that could harm the beneficial bacteria. If you stick to these
rules you can create a healthy system of ‘good’ bacteria in your
aquaponic system. Bacteria need a lot of surface area to thrive—raft and
deepwater culture systems have enough surface area for the beneficial
bacteria to grow but systems such as NFT (nutrient film technique) do
not. In NFT systems you have to help the bacteria by creating a
biofilter, which can be accomplished by adding a separate chamber to the
system that the waste-filled water will have to pass through. In this
chamber a piece of mesh should be strung from side to side, providing
adequate surface area for the bacteria culture. You could buy bacteria
and add them to your system but this is not really necessary as they
will develop and grow naturally if allowed to.
For beneficial bacteria to thrive a neutral pH balance of seven
should be maintained, unlike hydroponic systems where the pH should be
kept slightly acidic at a level of 5.8 to 6.8.
Environmental benefits
There are many reasons to
choose commercial and small-scale home aquaponic systems over
traditional methods of farming fish and vegetables separately.
Environmental concerns are one big reason that aquaponic systems are
being looked at seriously as an important future source of
food—aquaponics will eliminate the need for the costly synthetic
nutrients that are often used in hydroponic systems. These synthetic
nutrients are made using fossil fuels and many experts believe that we
have reached the peak level of oil production. This is a controversial
topic and is very debatable, but either way these fossil fuels could be
better used in other ways, such as heating and powering homes.
Another environmental benefit aquaponic systems have over other
farming options is that you don’t use pesticides when farming with
aquaponics. Pesticides that are normally used to control and eliminate
insects are harmful to the fish in aquaponic systems. Although most
pesticides in use today are considered relatively safe, there are many
that are not—and not all countries enforce the same strict pesticide
laws that protect us in North America.
Aquaponics is also advantageous in that it conserves water. Fish
farms must either use expensive filters to purify water before it is
recirculated, or—more likely—dirty water is just flushed and fresh water
is then used to replace it. Water used in hydroponic systems must be
replaced often as well—salts and minerals that are not absorbed by the
plants can build up, reaching toxic levels quickly. In aquaponic systems
plants absorb the fish waste, acting as a natural filter. In this way
water can be continuously recirculated, only occasionally needing a
top-up to make up for evaporation and plant transpiration.
The capability of aquaponic systems to recirculate water efficiently
could be very beneficial in arid regions of the world where so many
countries are now facing drought and food shortages. Aquaponics looks
like it could be a great solution to those problems—by recirculating
water, aquaponics systems should allow people to grow more food with
less water. Since aquaponics doesn’t require synthetic nutrients or
pesticides either, it can be a very cost-effective means of feeding many
people. Aquaponics could also be established on a large scale outdoors
in warmer climates to utilize the sunlight.
People love fish—it is highly nutritious and at one time the supply
of most species was so plentiful as to appear inexhaustible. Now, due to
overfishing, climate change and lax regulations the world’s stocks are
rapidly dwindling and it seems more and more likely that fish farming
will have to become the way of the future. If we are serious about
finding a sustainable way for future generations to acquire the
nutrition that fish can provide, we must take a long look at aquaponics.
The world continues to change and the population is going to keep
growing. Climate change and ever-expanding urban sprawl are taking away
fertile land that was once used for agriculture. Fish stocks are
plummeting, while large-scale farming on land reduces the natural
habitats of animal species. We are at a vital crossroads and the
well-being of future generations depends on which road we take—it’s
beginning to seem more obvious every day that aquaponics could be a very
important part of the solution to our planet’s impending food
shortages.
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