Aquaponics is a system of cultivation that is starting to become much better
known, both in terms of commercial agricultural production and the smaller
scale of the permaculture gardener. It is appealing to both because it is a
system that requires very little input in order to function well, and produces
two types of food product“ plants and fish.

Aquaponics uses a linked system of fish tanks and vegetables beds. The only
inputs needed are food for the fish and a method to pump water around the
system (gravity can be used one way in some circumstances, but even then a
pump will be required to complete the cycle). The basic system involves
pumping the water from the fish tank, complete with the droppings of the
fish, into the vegetable beds. The plants use the nutrients from the
droppings that are in the water, and in doing so filter the water so that
it is clean enough to go back into the fish tank.

There are
three major forms
of aquaponics systems

Media Beds

The media bed aquaponics system is probably the easiest to set up on your
permaculture plot. It consists of garden beds filled with small porous
rocks typically clay pellets – into which the vegetables are planted
(this is a no soil system). Water from the fish tank is either pumped or
drained via gravity, depending on the specifics of your site, into the
beds so that the plants can access the nutrients. The rocks are porous
to allow them to hold water for longer for more efficient nutrient uptake,
and to remain aerated. The rocks also serve to filter out biological
organisms such as parasites to prevent them going back into the fishes’
water, as well as any solid material (plants take up nutrients in a
dissolved, soluble form, so any solids would not be used and hence
contaminate the water if they returned to the fish tank). The clean water
drains into a container below the garden bed, and is then pumped back into
the fish tank.

The garden bed can either have a continuous flow of water moving through it
or is alternately flooded and drained, using a siphon to drain the water
when it reaches saturation point. The media bed system can be used on a small
or large scale and provides good plant support. The major disadvantage is that
the rocks used to fill the beds can be quite and expensive initial cost.
Permaculture gardeners choosing this system must also keep an eye on the pumps
so that they don’t get blocked with fish waste, and ensure that with either
the continuous flow or ebb and flow systems, no part of the garden bed becomes
waterlogged, as this can cause it to become anaerobic and affect plant growth.

Nutrient Film Technique

The nutrient film technique involves siting a series of pipes adjacent to the
fish tank and pumping water through them as a very thin film. The water moves
slowly allowing plants, which have been placed in holes in the pipe, to access
the nutrients within. When the water reaches the end of the pipes, it is pumped
back to the fish tank. Because there is no solid material or surface of the
water open to the air, extra filtration equipment is needed to clear the water
of solid and biological waste before it is returned. However, the system is very
efficient in its water use.

This system is probably best used in large-scale aquaponics system, and has the
disadvantage of being unable to support larger, heavy plants, such as tomatoes
and cucumbers, which can be utilized in the media bed system. It is primarily
used to cultivate leafy greens and salad greens, which have small root systems
and are relatively lightweight.

Deep Water Culture

The deep-water culture system is sometimes referred to as the deep flow system,
and involves siting the plants on rafts through which their roots protrude and
hang in the nutrient-rich water from the fish tank. The water must be filtered
of any solid waste before reaching the plants, but aside from that, the equipment
required is minimal and can be sourced cheaply. While commercial operations often
use specially constructed channels to hold many rafts (allowing for ease of harvest,
as well as capacity for higher yields) the system can easily be used in permaculture
gardens. Simply punch holes in the base of a Styrofoam container, plant your crop
through them, and float on the surface of the fish tank, with the filtrations system
attached. Just ensure you stock your tank with fish species that are not voracious
plant eaters, so they do not decimate the roots.

This system has the advantage of a more stable environment for both the plants and the
fish. Because the water is not moved from the fish tank into other systems, it does not
experience fluctuations in pH or temperature.

Whichever system you use, there are many fish species that you can choose to stock your
aquaponics system with, from catfish and tilapia to carp and crustaceans. Set up costs
can be minimized by using recycled containers for your fish tank (making sure they are
thoroughly cleaned before stocking) and garden beds. You will also need to ensure that
the water is oxygenated. Because a fish tank is a static body of water, it needs a pump
to force air into it and provide the fish with sufficient oxygen. When sourcing food for
your fish, try to ensure that it comes from an organic sustainable source. One of the
major pressures on wild fish stocks is the use of small fish to make fish food for
captive stocks. This not only throws wild ecosystems off balance, but it is an inefficient
use of resources, with several grams of fish needed to make just one of fish food. Some
enterprising permaculturists have combined livestock resources by sting their chicken coop
above their fish tank, so the chickens’ dropping provide food for the fish, and the
gardener only needs expend time and energy on the harvesting!

3 Types of Aquaponics Systems


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