AQUAPONICS SYSTEM

Aquaponics

Introduction

Aquaponics or pisciponics is a combination of hydroponics, the growing of crops in water rather than soil, and conventional aquaculture, the raising of aquatic animals such fish. The fish waste provides organic food for the growing plants and the plants naturally filter the water in which the fish live. This is a mutual relationship where the fish provide food for the plants and the plants provide a clean environment for the fish. Fish waste is used as fertilizer hence there's no need for buying chemical fertilizers.

Advantages of Aquaponics:

·            Water use is reduced significantly in recirculating aquaponics

·            No need for chemical fertilizers as fish waste is used in cycle

·            Less land space required – plants and fish are grown in close quarters.

·            Can grow food all year round depending on climate and the location of the aquaponics system (inside/outside)

·            Faster growth of plants (can exceed hydroponic plants growth by up to 4 times for particular vegetables and herbs.

·            Lower susceptibility to disease plants e.g. soil-borne bacterial disease. Fish in aquaponic systems are also less susceptible to pathogens that are common to aquaculture systems.

·            Saves labour and Money (no weeding, fewer pests, no watering, and fertilizing, bending, digging. Feeding the fish is what is important in aquaponics.

Disadvantages of Aquaponics

Cost of investment is higher than other forms of farming

Technologically requires more expertise to run properly.

How Aquaponics Works

The 2 major components of aquaponics systems are the fish and the plants. The natural characteristics and requirements of each of these components support the growth and health of the other.
 

Role of Aquatic Animals such Fish

·          Fish digest their food and create excrement which is released into the water where the fish is reared. This excrement is rich in nutrients that plants need to grow and produce.

·         In this process is there is ammonia in the fish waste which is toxic to fish in high concentrations and needs to be removed or the fish will die. The ammonia is broken down into nitrates and nitrites which are nutrients required by plants.

·         The invisible actors in this symbiotic relationship are the beneficial bacteria and composting red worms. The beneficial bacteria (Nitrosomonas and Nitrobacter) exist on every moist surface of an aquaponic system.  They convert the ammonia from the fish waste that is toxic to the fish and useless to the plants, first into nitrites and then into nitrates. The nitrates are relatively harmless to the fish and are important plant nutrient

·         The worms convert the solid waste and decaying plant matter in the aquaponic system into compost.

·         The water is reticulated from the tank through growing beds where the plants are grown. The plants take up the nutrients and use them to create energy for growth. The water flows back into the fish tank in a continuous cycle.

Hydroponically grown plant

·   Nitrate-rich water is introduced to the hydroponically grown plants.  These plants are placed in beds that sit on tubs filled with water, and the water is enhanced by the nitrate harvested from the fish waste. The plants' bare roots hang through holes in the beds and hang in the nutrient-laden water.

·   The hydroponic plants' roots function as a biofilter in that they strip ammonia, nitrates, nitrites and phosphorus from the water. The circulation of the water takes the nutrients away from the fish, to the plants. The water that returns to the fish tank is free from the nitrates and nitrites that are not required by the fish.

Site selection
Choosing the right environment in which to place the aquaponics farm is important. The amount of sunlight, ambient temperature, rainfall and wind are all crucial factors in producing a healthy plant. When growing outdoors, choose varieties of vegetables that will grow best in the environment. Most areas will require the use of a greenhouse, or you can always grow indoors.

Deciding What crop to Grow

• Different plants grow under different conditions. It’s important to consider which type of growing bed to use. This is determined by the type of root structure that plant tends to have.
• Plants with no root structure need floating beds, while root vegetables grow better in wicking beds.
• Most of the vegetables grow best in media beds. However plants such as lettuce, herbs or leafy greens, floating “raft” style beds are ideal. For root vegetables, wicking beds are a better choice. If you plan to grow tomatoes, peppers, beans or most other types of multiple yield plants, media beds are is the best option.

Selection of fish type

The choice of what to produce will be guided by:
1) Ecological requirements of the species- The different species have different biology and therefore different ecological requirements. They will therefore have different feeding, breeding and water quality requirements.

• Consider the temperatures at which they fish species thrive and survive. Tilapia, catfish are the main type of fish reared in Kenya for food. Other types are ornamental fish e.g. gold fish and koi carp that are not consumed.
• Nile tilapia and African catfish require warm water of more than 25- 28°C. In Kenya, such regions are to be found in low land areas. High sunlight intensity is also preferred for tilapia culture under semi-intensive production.
• Trout require cold water of less than 18°C for growing out and below 10°C for hatchery production. Such conditions in Kenya are to be found in high altitudes areas.
  2) Market preference

3) Production technology of the species
4) Resources available to produce

Management Challenges

• Water quality is a high priority and insures the growth of healthy fish and plants. There are several factors that go together to create the perfect water environment. They include the pH, Ammonia, Nitrite, Nitrate, Bacteria levels, Temperature, Oxygen levels and Alkalinity and Source. An imbalance of any one of these factors can cause the water quality to drop to harmful conditions for the fish and/or the plants.
• If waters get too hot especially when exposed to the sun during hot days, there will be a lack of oxygen for the fishes.
• Ammonia is very toxic to fish and a build-up of it in the fish tank will kill them (dead fish will also produce ammonia).
• The size of your fish tank and the amount of fish in the aquaponics system will affect the efficiency of the system e.g. having a dense population of fish can result in the bigger fish feeding on the smaller fish or too much fish waste for the biofilter to effectively convert to nitrates.
• The most common diseases in fish are bacterial infections, fungal infections and parasites. Aeration and water movement are critical for keeping fish healthy, as well as keeping the water clean and free from buildup of solids. Different fish suffer from different diseases. If problems with pests occur, no pesticides can be used, as they affect the health of the fish. Pest/diseased affected plants are removed from the system, and replaced.  

Word of Advice to potential Aquaponic Farmers

Potentially an aquaponics system is more productive than a traditional system, but it is also susceptible to greater risks.  There is need to prepare well, and to be properly informed before risking a considerable investment in money and time.