Aquaponics:
A Hydroponic and Aquaculture Ecosystem

Horticulture and the Science of Plants
Horticulture Youth Adventure Program

David Wm. Reed, Instructor
Texas A&M University
BACKGROUND
Hydroponics means water culture and is growing plants with their roots submerged in water.  Air is bubbled through the water solution to supply the roots with air.  Fertilizers are dissolved in the water to supply the plants with all the nutrients they need.
Aquaculture is growing fish in water culture.  Shrimp and other aquatic animals can also be grown.  The water is bubbled, sprayed in the air or circulated to supply the fish with air.  They are feed specially prepared food.  The water has to be filtered and treated to remove or modify toxic compounds produced by the fish  waste.  The main problem is that fish waste produces a lot of a nitrogen compound called ammonia (NH3). Ammonia is toxic to fish and plants at high concentrations.  So the aquaculture system needs a bioreactor to get rid of the excess ammonia.  A bioreactor is container filled with very porous gravel or plastic, and the water from the fish tank is poured through the bioreactor.  Bacteria start growing on the porous material, and they break down the ammonia.  The type of bacteria that do this are called nitrifying bacteria (Nitrosomonas and Nitrobacter), and they convert ammonia (NH3) to nitrate (NO3).  Nitrate is not toxic to  fish or plants and is an excellent plant fertilizer. 

If one combines hydroponics (growing plants in water) with aquaculture (growing fish), then you have  aquaponics.  Aquaponics uses the water and wastes from the fish tank to supply the fertilizers, especially the  nitrogen, needed to grow the plants. An aquaponic system is a sustainable ecosystem, and if we harvest the fish or the plants for food it would be called sustainable agriculture. Saying something is sustainable means that it can survive on its own.  A sustainable ecosystem or sustainable agriculture is where plants and or animals are growth with recyclable resources so a lesser amount of inputs, such as fertilizers, are needed.   All we have to do is feed the fish and the fish and  plants survive very well together.  We do not have to spend money on fertilizers.

In our aquaponic system, we are going to raise the tropical fish tilapia, and grow a variety of  vegetables and flowering plants in a hydroponic trough culture.
Overview of the Aquaponic System Used by the Class
(for detailed view go to Aquaponic System)
 
Our aquaponic system  is a combination of a aquaculture fish tank and a hydroponic trough growing system.  The bioreactor removes toxic levels of ammonia.  Instead of pumping water directly out of the fish tank into the bioreactor, the water in collected in pump tank (a holding tank with a water pump), then pumped into the bioreactor; this facilitates settling and removal of solid fish waste.  The water from the bioreactor can be diverted to drain back into the fish tank or to the hydroponic troughs.

TAKE HOME LESSONS
1) To learn how to set up a hydroponic system to grow plants.
2) To learn how to set up a aquaculture system to grow fish.
3) To learn how to combine hydroponics and aquaculture to make an aquaponic ecosystem.
4) To learn how to monitor the water so toxic waste do not accumulate from the fish and make sure there are enough fertilizer nutrients for the plants. 
5) To compare how plants grown in a traditional hydroponic system compared to an aquaponics system. 

MATERIALS NEEDED
Fish tank, hydroponic tank or trough, water pump, air pump, bioreactor container. 

PROCEDURES

1) Feed fish daily.
Every day we will feed the tilapia with special tilapia food pellets.  The fish should be feed daily with a weight of food equal to 5% of the weight of the fish in the tank.  However, the fish should not be feed more food than they can eat in one half hour.

2) Conduct an experiment to compare growth of plant in aquaponics versus traditional hydroponics.

Experiment
We will grow plants in recirculating troughs comparing: 
1) water from the fish tank/bioreactor in the aquaponics system, and 
2) a traditional hydroponic solution made with fertilizers.

Objective
The objective is to determine if  water from the fish tank/bioreactor has enough nutrients from the fish waste to grow plants without fertilizers.

Setting Up the Experiment
You will be supplied with young seedlings.  Insert a seedling in the holes of the hydroponic troughs.  Insert the seedlings so that the roots are in the water solution in the trough.  We will use two types of plants, such as bean and chinese cabbage.  We will use at least five of each type plant in both the aquaponic and the hydroponic trough.

Daily Measurement of  Water Quality
Every day will use instruments to measure  the following in the recirculating water:
1) ammonia with an aquarium ammonium kit
2) nitrate with a nitrate meter
3) pH with a pH meter
4) salts with an electrical conductivity meter

We will write down the measurements on a Daily Log of Water Quality data sheet and calculate the averages.
We will compare the measurements to standard tables to determine if  the ammonia, nitrate, pH and salts are within acceptable ranges or if they are becoming toxic.

Daily Measurement of Plant Growth
Every day will measure the following:
1) height of each plant
2) number of new leaves formed that are longer that 0.5 cm (about 1/4 inch)

We will write down the measurements on a Daily Log of Plant Growth data sheet and calculate the averages.
We will compare the growth of the plants grown with the water from the fish tank/bioreactor to the plants grown with the hydroponic fertilizer solution.

 
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