What is aquaponics? Advantages and disadvantages.

Aquaponics is one of the top urban farming methods that is an integration of aquaculture and hydroponics. Aquaculture is the rearing of aquatic animals like fish in a closed and controlled artificial environment.

Fish are reared in circular or rectangular plastic tanks where they are provided with pellet food and water parameters like oxygen levels, solid concentration and carbon dioxide are kept constant.

Hydroponics refers to the growing of plants in a soilless nutritious medium. There are different hydroponic systems though in them all plants receive nutrition via their roots

How aquaponics operates

The fish in the tank consume feed and excrete nitrogenous waste into the water. The waste water along with the uneaten food is the pumped to the bio filter unit from where it is broken down broken down by bacteria and fungi into simpler nutrients.

Nutritious water from the bio filter is then pumped into the hydroponic   unit where the growing plants use the nutrients for their growth. In doing so, the plants help to clean the water. It is then pumped to a reservoir after some time and pumped back to the fish growing system.

Fish reared include;

• Striped bass
• Tilapia
• Trout
• Cat fish
• Gold fish
• Koi

Plants grown in the hydroponic unit include;

• Leafy vegetables like Chinese lettuce, cauliflowers, basil, microgreens, kale,
• Small plants like strawberries and cherry tomatoes
• Herbs

NB; It is very important to note that the plants grown in aquaponics have very minimal nutrient requirements.  

1.Fish tanks

This is where the fish are raised and live. The tanks can be rectangular or circular and are usually made of plastic. Optimum water conditions for the growth of fish are kept maintained at all times like PH, oxygen levels and temperature. An air stone is put in the water to keep it oxygenated and feeding is done at regular intervals.

2. Bio filter

Water from the fish tank containing nitrous waste and uneaten food is broken down by nitrifying bacteria (nitrosomonous and azotobactor) and fungi into simpler compounds from here. excess solids are also removed from here. The water is then pumped to the hydroponic unit.

3.The water pump

This is used to move water along the system and distribute it to the individual components.

4. Hydroponic unit

This is where the plants are grown. The major hydroponic systems used in aquaponics are;

1. Deep water raft system

This is the most popular system used even by most commercial aquaponics farms. The plants in a large container float in a foam raft structure with their roots dangling into the nutrient-rich water from the biofilter that flows at the bottom. The plants’ roots are supposed by mesh pots.

2. Nutrient film technology

Here nutrient water from the biofilter is made to go down along a slopping channel where the nutrients are absorbed by the plant roots.

The plants are arranged equidistantly in a row with the crown above and the roots in the channel.  Mesh pots are sometimes used to support the plants and in some instances, media like gravel can be used to support the roots. The NFT is used in commercial indoor vertical farming to grow leafy vegetables.

3. Media filled beds

Here containers are filled with porous stones or clay pellets that facilitate plant growth. Water from the biofilter is then pumped into the system to provide nutrients for plant growth.

4. Vertical aquaponics

Here tower systems, PVC NFT pipe channels and vertical deep water culture units are used to grow plants while stacked in rows on top of each other.

Advantages of aquaponics

• There is double output; fish from the tanks and a regular supply of fresh vegetables.
• The system is easy to maintain and manage.
• Aquaponics saves water and facilitates water recycling since its reused compared to normal farming methods.
• Aquaponics can be carried out anywhere in the world even in arid no arable land places.
• The output from the system is entirely organic without pesticides, herbicides or chemical fertilizers.
• It is easy to control pests and diseases.
• There are no weeds
• The system is environmentally friendly.

Disadvantages of aquaponics

• It requires daily maintenance to manage; feeding the fish, cleaning the tanks, maintaining adequate water conditions for the fish like temperature, carbon dioxide, PH, solids concentrations, and PH.
• Initial startup costs can be high for some people.

Bottom line

Aquaponics is a great way to simultaneously farm greens and grow vegetables. The benefits are many and DIY units can be made by farmers and people to practice hydroponics at a small scale and also at home in their backyards.