Over the past years, there are already several types of Aquaponics systems developed and most of these are just improvements of an earlier recognized method of food production known as Hydroponics. While these techniques were just borrowed, the enhancements made it very suitable for use with Aquaponics systems.
Each of these types can be used in different ways to suit the needs of an individual or a group. For instance, a backyard system will be very much different compared to a commercial system in terms of components used and the need for circulation and aeration. The basic components common to any sytem is a grow bed, a fish tank, a pump and standpipes or siphons to drain water.
The three most common and widely used types of Aquaponics systems are the Nutrient Film Technique, Deep Water Culture and the Media Based Method. Here is a description of each one.
NUTRIENT FILM TECHNIQUE (NFT)
This technique is very popular in Hydroponics, but is less used in an Aquaponic system. In this method plants are grown in long enclosed gutters or PVC pipes with plants set in plastic cups, allowing the roots to absorb nutrients from the water. The water is being pumped down the gutter in a very thin film, just enough to supplement the plants’ needs. The water is then circulated back to fish tank after it has passed the plants. It is of utmost important however that the Aquaponic fish tank water is filtered before sending it through the NFT pipes. Uneaten fish feed and fish poo might clog up the pipes and the plant roots which can cause an anaerobic condition. This condition might harm both the plants and the fish. It produces a foul smell, too.
Though this might not be a favored method in Aquaponics, it has several benefits to offer. This method does not require a lot of fish yet can be very productive. Because of its design, the plants are exposed to enough amounts of water, oxygen and nutrients which encourage rapid and healthy growth of plants.
A couple of recognized drawbacks of this method are constant maintenance and monitoring because the water is very vulnerable to temperature and pH changes. Also, this method really requires bio filtration since there is not enough surface are for beneficial bacteria to break down the ammonia to oxygen.
RAFT or DEEP WATER CULTURE (DWC)
This is a method more commonly employed in commercial operations and a technique borrowed from Hydroponics. A simple DWC set up consists of plants floating on top of the water, allowing the roots to hang freely and absorb the nutrients from the water. A better DWC method however already requires filtered water from the fish tanks to be pumped into channels of floating rafts. These floating rafts have plants floating on the water surface with their roots immersed in water. A filtration system is really vital in this method as solid wastes can cover the roots which can inhibit the plants from getting the nutrients and oxygen they need. A pretty simple and straightforward DWC set up consists of fish grown in tanks with water being pumped through a filtration system and into channels of floating rafts with plants which roots hang freely to absorb the nutrients from the water. The water then is drained back to the fish tanks to be used again.
The primary advantage of the raft or deep water culture method is that it yields good production of leafy vegetables and herbs which is why this more frequently used by commercial farmers. There are also plenty of surfaces for the beneficial bacteria to grow. The large volume of water involved also helps in maintaining water temperature and pH stability.
Like other systems, this method also has a few downsides such as the utilization of filters to remove solid wastes and the difficulty in raising larger plants such as tomatoes and cucumbers.
MEDIA BASED METHOD
It is considered as the simplest type of Aquaponic system. It uses tanks or containers filled with growing media like expanded clay balls, pebbles or gravel which at the same time act as biological and mechanical filters. Periodically, water from the fish tanks are pumped over the bed and drained back to the fish tanks once an appropriate level of water is reached. This will continue on a cycle and the wastes coming from the water will be left and broken down in the grow bed. This will provide nutrients to the plants without using pesticides, herbicides and fertilizers. We also call this as the ebb and flow or the flood and drain way of employing the media based method. Another recognized way of operating this type of Aquaponic sytem as well is by ensuring a continuous flow of water over the rocks. This is known as the constant flow and constant drain method.
Several people prefer this type of system because it costs less to start up and has less maintenance compared to others. This is the reason why it is more popular for backyard Aquaponics enthusiasts. This method also provides better plant support because it uses media to grow the plants. Also, the use mechanical and biological filtration is no longer necessary because the media bed already acts as filter.
The drawback of this is that all the solid wastes coming from the fish tanks end up in the media bed which can cause a clog over time and will need to be cleaned. The type of media being used can also be expensive.