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Aquaponics

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Overview

Aquaponics Aquaponics is a growing system that integrates aquaculture (raising fish) with hydroponics (growing plants without soil). This symbiotic relationship is good for maintaining a sustainable form of agriculture. Good bacteria forms, which then converts the toxins, produced from fish waste, into nutrients used by plants. By absorbing this nutrients the plants filter the water, giving the fish a livable environment. This cycle helps keep the tank in good shape for both fish and plants.

This system is as organic as you can get. With this set up, there is no need for fertilizer because the fish waste is all that is necessary for the plants to grow. Herbicides also isn't needed because there is no soil used to grow the plants. This system is especially great for areas with poor soil quality since there isn't any soil needed. You can grow large quantity's of plants in small areas, without wasting a large amount of land. Aquaponics is a great way to sustainably grow fresh fish and vegetables for a family, to feed a village, or generate a profit in a commercial farming volume. Not to mention the fact that you can produce your own dinner and side dish in one system. The best thing, is that when your fish get to big, you can eat them!

Comparison of Methods

In order to really understand aquaponics it is imperative to understand that it uses both methods of aqua-culturing and hydroponics to grow its sustainable crops. By learning about the two methods you can fully appreciate the advantages and disadvantages of these three farming methods.

Aquaculture

Aquaculture is the farming of aquatic organisms such as fish and shellfish. This is a specialized form of growing where fish are raised in tanks, which are normally densely packed. Since there are such high quantities of fish together, the amount of waste accumulates at an enormous rate. In order to keep the ammonia levels down and prevent diseases, different forms of filtration need to be running constantly.

Hydroponics

Hydroponics is a method of growing plants in a mineral water solution with no soil. This system allows for a more efficient growing method that is equipted with less space, less labor, and water. Since the plants are in ideal water conditions they don't need excises water, where normally much of the water is wasted.


Types of Advantages and Disadvantages

Advantages Disadvantages
Organic Farming *Organic farming has become popularized in the marketplace because it is presumed to be a healthier way of growing food.
*Utilizes wastes for fertilizer.
*Uses natural pest control.
*Biological system produces better tasting and, sometimes, more nutritional crops.
*Uses more land than traditional farming.
*In most cases, it costs more to grow and certify organic crops than other methods of farming.
*USDA certification is losing value as agribusiness replaces small-farm organic production.
Inorganic Hydroponics (uses mined and manufactured fertilizers) *Produces a high volume of crops in a small space.
*Combining it with controlled environment agriculture results in consistent, year-'round production.
*Dependent on manufactured and mined fertilizers that are costly, rising in price and becoming harder to get due to increased demand worldwide.
Recirculating Aquaculture *Produces large volumes of fish in a small space. *Recirculating systems have a high rate of failure due to high stocking rates and low margin for error.
*Produces large waste stream.
Aquaponics (Organic Hydroponics) *Aquaponics has all of the advantages of organic farming, hydroponics, and aquaculture! Plus:
*Fish waste provides fertilizer for plants.
*Fish do not carry the pathogens, such as e-coli and salmonella, which warm-blooded animals do.
*High water volume in raft aquaponics reduces risks for fish production.
*Aquaponics demonstrates a natural cycle between fish and plants and is the most sustainable of the four methods presented here.
*With consistent bio-mass in the fish tanks, plants thrive.
*Management requires someone trained in raising both fish and plants.
*A major loss in the fish tanks can disrupt plant production.

Aquaponic Food Production: Raising Fish and Plants for Food and Profit, Rebecca L. Nelson with contributions from John S. Pade

Fish

Fish as Food

Depending on the climate you live in, it is best to use fish which are native to your area. This allows for the least amount of energy to be put into heating or cooling the fish tanks. It is also recommended to choose a hardy breed of fish that can survive fluctuations in water quality or temperature. Keep in mind that some fish eat their companions when they become larger, and must be sorted out into separate tanks. [1]

Feeding

Fish food is the primary input into an aquaponic system, so choice of food is crucial for sustainability. [2]Feeding your fish can be done with a high-quality pelt food made of fish and soy. However, one of the advantages of an aquaponics system is that it is a closed loop. So, food can be produced in the grow beds, if the chosen breed of fish will eat leafy greens. Duckweed is also an excellent choice as it can be grown on the surface of an auxiliary tank, and harvested and frozen as needed. [1]

Nursery

Although fingerlings can be purchased, they need not be the only source to populate the fish tanks. To continue with the idea of a closed-loop system, a nursery tank can be set up and mating facilitated so that the fish population will sustain itself. It is important to move the young to a separate tank in some cases because the adults will eat them. [1]

Plants

Wild plants.jpg

Appropriate Choices

Root Crops

Despite growing in a rocky medium, such as clay pebbles or gravel, root crops are said to do reasonably well in an aquaponics system. A short list of plants that could be grown in with aquaponics would consist of lettuce, chives, watercress, basil, cabbage, tomatoes, squash, and melons. Early on in the development of aquaponics, it was thought that only leafy crops could be grown. Now, over 60 different types of food have been grown successfully, as tried by the Crop Diversification Center in Alberta, Canada. [2]

Invasive Roots

It is not advisable to plant a species with fast growing roots, such as mint. An aggressive root system will grow into the piping and overtake the system.

The Media-Filled System

Because media-filled systems are most common for at-home food production, this section will be elaborated upon, as it pertains to the media-filled method. Many components of this method are also used in raft and NFT systems. The basic pieces of a media-filled operation are the grow beds, the fish tanks and a clarifier. Of course, individual pumps, aeration mechanisms, back up power systems and a variety of pluming using PVC piping are also needed.

Growing Medium

A standard gravel or hydroton, a type of clay pebble commonly used in hydroponics, can be used as growing mediums. Gravel is slightly less expensive, but the hydroton allows for easier planting in some cases because of its uniformity.

Volume

One fish needs about 10 liters, or 2.5 gallons of space to itself. So, if you have a 50 gallon fish tank, you can have 20 fish. The more water you have, though, will help to stabilize the system. The minimum recommended tank size is 250 gallons, or 1000 liters. The grow bed volume should be the same as the fish tank volume. [1] Smaller systems have been made with varying degrees of success.

Flush/Fill System

When using a grow bed, the media must be periodically flooded and drained. There are several methods by which this can be accomplished.

Flow Rate
Bell Syphon
Spill-over

Water

Filtration

Clarifiers, Mineralization, De-gassing, and Biofiltration

The middle barrel in this system, which has been buried in the ground, acts as the clarifier. The grow beds are raised behind it, and the fish tank is buried in the front. Personal photograph by author.

The maintenance of water quality is critical for all parts of the system. One particularly important factor is this is the pH balance, because different parts of the system thrive in a certain pH. Therefore, some compromises must be made. Fish generally like a pH of 7.5-8, while plants do best at 6.0-6.5, and the bacteria colony works most efficiently at 7.0-8.0. The consensus for an overall pH is 7.0 for the system to function at its best. [2]

Reaching acceptable water quality levels requires different components depending on what type of aquaponic set-up is installed. There are three main types: raft, Nutrient Film Technique (NFT), and media filled beds. Raft systems, also called float, deep channel, and deep flow, grow the plants in floating styrofoam boards in a tank separate from the fish tank. NFT grows plants in long, narrow channels with a thin film of water flowing through them to bring nutrients to the plants' roots. Media filled beds are simply containers filled with a growing medium, like gravel, perlite, or clay pebbles, in which the plants roots are held, then they go through a flood and drain sequence to bring nutrients to the roots. [2] The first two methods are more common in commercial-size operations, while the last method is most commonly used in backyard operations, producing food on a small scale to feed about one family.

A clarifier is used to remove solids from the water column. This can be done in multiple ways. Conical clarifiers and settling basins facilitate the solids settling out of the water column; they are based on the concept of high specific gravity, compared to the water they are in.[2] Basically, this means they sink and can be captured at the bottom of a clarifying instrument, whether it be a settling basin or a conical clarifier. Another way to remove the solids is a micro screen drum filter that removes organic matter in a backwashing process. Removing solids is only necessary in the raft and NFT systems because in a media-filled bed, the solids are caught in the media, where they can then biodegrade without interfering in the function of any other system components. [2]

Now, you might be wondering how the system functions if the solids, which are essentially the fertilizer of the system, are removed. Before the clarifier, raft and NFT systems need a mineralization tank that is filled with some type of porous media. In this area, heterotrophic bacteria convert the waste into elements that are readily used by the plants. This process also creates gases such as hydrogen sulfied, methane, and nitrogen. Therefore, a degassing tank is needed to help release these into the air. [2] Again, this is not needed in a media-filled bed because the solids remain in the system trapped in the media.

Biofiltration provides a place for the bacteria colony to live. It is not necessary in raft and media-filled systems because there is enough surface area for the bacteria to colonize to a healthy level. However, in a NFT system, extra colonization space must be provided for a healthy colony to stabilize. This extension is called a biofilter. [2]

Bacteria Colony

The bacterial colony that inhabits the entire system is responsible for the conversion of nitrites and ammonia to nitrates, which can then be used by the plants. Without this conversion, the nitrites, and to an extent the ammonia, would reach toxic levels and kill the fish and plants. Specifically, nitrosomonas sp converts ammonia to nitrite, and nitrobacter sp converts nitrite to nitrate. [2]

Building up the Natural Colony

These bacteria are naturally found in the air and water, they need not be added to the system. A buildup of the natural colony can take 20-30 days, [2], sometimes up to 8 weeks. Eventually, as all natural systems, the components will fall into balance and remain stable with little upkeep.

Starting Your Own

However, to expedite the colonization process, a uria fertilizer can be added in very small amounts as a source of ammonia. [1]

Home Built Systems

There are many ways someone can build an aquaponics system at home. It can be a fun and rewarding project especially if it is used to teach children about the life sciences. Investing in a home built system for food production purposes is a different thing entirely. There are many things that can go wrong in a Aquaponic system because there are so many variables to the system. Water quality is the number one concern in aquaponics, and it can suffer major changes if just one piece of the system is out of balance or malfunctioning. So it is important with this investment, like any other, to understand what the risks are before you begin a project. Outlined below are a few things to look out for and ways to help design an efficient system. But this, like any document, is incomplete. If you do decide to build your own system you will no doubt encounter new problems. Do not be discouraged though, solutions are out there and if you keep reading and keep working the answers to affordable food production are out there.

Water Quality issues and Snags

When designing a new system it is important to understand that water quality is going to literally be the life blood of the system. Without the proper flow rate and water conveyance, the system will function poorly if at all. In his instruction video Aquapnics Made Easy, Murry Hallam points out that in small aquapnocs systems it is best to not have a system smaller that 1000L (265 gallons). This is because below that the amount of water in the system is less stable, with less water to act as a buffer when temperatures vary, or when there is a spike in fish waste.

Moving that amount of water around can use up a lot of energy as well and so in designing a home built system, focus on ways to use gravity to promote water transfer form one part of the system to the other. A good way to do this in the planning phase is to draw diagrams that show just where the water level will be in each tank. This way you know where in the system to order things and at the end of the diagram how much vertical lift you will need to achieve in order to move water though the system.

  1. 1.0 1.1 1.2 1.3 1.4 Murray Hallam's Aquaponics Made Easy, Flashtoonz Films, 2009
  2. 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 Nelson, L. Rebecca. "Aquaponic Food Production: Raising fish and Plants for Food and Profit." Montello: Nelson and Pade, Inc, 2008.