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Past Articles Library | Gardening Design | Aquaponics Versus Hydroponics

Aquaponics Versus Hydroponics

Aquaponics and hydroponics have been in the news lately.  However, many people are confused as to what each method of growing plants consists of.  This article will look at what aquaponics and hydroponics each consist of so you can make an informed decision about whether you want to give them a try.

Hydroponics are the simpler of the two systems.  In hydroponics, plants are suspended with their roots in a nutrient rich water solution.  This used to be used primarily by marijuana growers but it has now gone mainstream.  This is called the nutrient film technique (NFT).  It is very popular and works well.  However, there are several other ways to grow plants in hydroponics.

Another technique is to place the plants in an inert growing medium such as Rockwool, perlite, vermiculite, coconut fiber, gravel, sand and many more.  These mediums do not contain any nutrition.  Water and fertilizer are delivered to the plants in a highly soluble form exactly when the plants need them.  It even contains all the trace elements the plant needs.  The water and nutrient solution is so easy to uptake that the plant does not have to spend a lot of its energy growing roots.  This allows the plant to concentrate on growing foliage and vegetables, not roots.

One factor that is extremely important to control is the pH of the solution and water the plants get.  Plants grow best in varying pH ranges.  Some pH values make it difficult or impossible for the plant to absorb the micronutrients that the plant needs to survive.  When this happens, plants get sick and do not grow well.  It is very important to know the pH range your plants grow best in and to keep the nutrient solution and water within that range. The best pH range is from 5.8 to 6.8, with 6.3 considered ideal.

You might wonder why someone would go to all the trouble of setting up a hydroponic system instead of just growing things in soil.  Plants that have been grown in a hydroponic system grow thirty to fifty percent faster than a soil grown plant.  The yield of the plant is also greater.  Scientists have found that the extra oxygen in the growing mediums helps stimulate root growth.  Plants with a lot of oxygen in their roots are able to absorb nutrients better.  With plenty of nutrients available, the plant grows faster and bigger than a plant grown in soil.

Hydroponic plants have fewer problems with bugs, funguses, and diseases.  This cuts down on the chemicals that must be used by conventional farmers to deal with these problems.

Hydroponic gardening uses considerably less water than traditional soil agriculture.  The solution that feeds the plants can be reused and recycled so fresh water is not needed as much.  In addition, the lack of pesticides is better for the environment.

Aquaponics is used to grow both plants and fish at the same time using the same inputs.  The fish are in a tank below the plants.  The water the fish are in is filtered to remove solid waste.  It is then used to water the plants.  Ammonia/ammonium in the water is converted to nitrite and then to nitrate by microbes living in the system. Nitrate is the type of Nitrogen that these plants can best absorb.  As the water is used to water the plants, they and the microbes filter it. This filtered water then falls back into the fish tank and keeps the fish alive.  The fish are fed pelleted fish food, which is the only major input in the system.  When the fish reach market size, they are removed and processed, then sold.  New fish are put into the system and it continues to operate.  A common fish that is grown in aquaponics is the tilapia.

For a small scale aquaponics venture, most people start with a tank under five hundred gallons.  Three hundred gallons seems to be the average.  It is best to have a circular tank with a central drain.  The circular design prevents fish from getting hung up in the corners and smashed by their fellows.  Figure on one pound of fish per ten gallons of water at final harvest.

It is important to only use bulk containers that are food grade and have been washed out well to hold the fish.  To prevent the fish from jumping out or getting stolen by a predator, the tank should be covered with something such as shade cloth, a screen, or netting.   Make sure that the covering does not block fish pellets from entering the tank.

The plant part of the system is done very much like a strait hydroponics system.  Plants are either planted in an inert medium and filtered water is pumped into them or they are planted with their roots suspended in the filtered, nutrient rich water.  The advantage of the inert medium is that it filters out the solids easily before the water goes back into the fish tank.  The disadvantage of this is that the medium must be cleaned periodically to remove built up solids.  Some systems use worms to eat the solids and convert them to a benign substance that the plants can utilize.

Aquaponics is rather complicated and the learning curve is rather steep.  It might also be expensive if you make a mistake and kill all the fish you were growing.  Starting with the hydroponics unit first and getting it running well is a way to lessen the steepness of the learning curve.  You can then add the aquaponics part of the system.  You will need to develop markets for both the fish you raise and your vegetable crop that you grow hydroponically.

At this writing, plants grown in a hydroponic or aqauponic system cannot be marketed as organic, even if only organic inputs are used.  The organic requirements reference the soil and since there is no soil, these systems do not meet the requirements for an organic designation.  Producers are working to change that.

For more information, you can go to the USDA aquaponics website where there are many papers detailing exactly what to do to get your system up and running.


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