Methods of Aquaponics

There are many different conﬁgurations of aquaponic systems. The components common to every aquaponic system are the ﬁsh tank and a plant bed. The variables include ﬁltration components, plumbing components, the type of plant bed and the amount and frequency of water circulation and aeration. Generally speaking, systems that utilize some ﬁltration to remove the solid ﬁsh waste will have higher production of ﬁsh and plants than those that don’t use ﬁltration.

There are three primary aquaponic methods emerging in the industry. Each if these methods is based on a hydroponic system design, with accommodations for ﬁsh and ﬁltration.

Raft System

In a raft system (also known as ﬂoat, deep channel and deep ﬂow) the plants are grown on Styrofoam boards (rafts) that ﬂoat on top of water. Most often, this is in a tank separate from the ﬁsh tank. Water ﬂows continuously from the ﬁsh tank, through ﬁltration components, through the raft tank where the plants are grown and then back to the ﬁsh tank.

The beneﬁcial bacteria live in the raft tank and throughout the system. The extra volume of water in the raft tank provides a buffer for the ﬁsh, reducing stress and potential water quality problems. This is one of the greatest beneﬁts of the raft system. In addition, the University of the Virgin Islands and other research programs have worked to develop and reﬁne this method for over 25 years. The raft system is a well developed method with very high production per square foot.

In a commercial system, the raft tanks can cover large areas, best utilizing the ﬂoor space in a green house. Plant seedlings are transplanted on one end of the raft tank. The rafts are pushed forward on the surface of the water over time and then the mature plants are harvested at the other end of the raft. Once a raft is harvested, it can be replanted with seedlings and set into place on the opposite end. The optimizes ﬂoor space, which is especially important in a commercial greenhouse setting.

NFT (Nutrient Film Technique)

NFT (Nutrient Film Technique) is a method in which the plants are grown in long narrow channels. A thin ﬁlm of water continuously ﬂows down each channel, providing the plant roots with water, nutrients and oxygen. As with the raft system, water ﬂows continuously from the ﬁsh tank, through ﬁltration components, through the NFT channels where the plants are grown and then back to the ﬁsh tank. In NFT, a separate bio ﬁlter is required, however, because there is not a large amount of water or surface for the beneﬁcial bacteria to live. In addition, the plumbing used in a hydroponic NFT system is usually not large enough to be used in aquaponcis because the organic nature of the system and “living” water will cause clogging of small pipes and tubes. NFT aquaponics shows potential but, at this time, it is used less than the other two methods discussed here.

Media-ﬁlled Bed System

A media-ﬁlled bed system uses a tank or container that is ﬁlled with gravel, perlite or another media for the plant bed. This bed is periodically ﬂooded with water from the ﬁsh tank. The water then drains back to the ﬁsh tank. All waste, including the solids, is broken down within the plant bed. Sometimes worms are added to the gravel-ﬁlled plant bed to enhance the break-down of the waste. This method uses the fewest components and no additional ﬁltration, making it simple to operate. The production is, however, much lower than the two methods described above. The media-ﬁlled bed is often used for hobby applications where maximizing production is not a goal.

Article: Methods of Aquaponics
Article Source: Pond Talk
Author: Sunland Water Gardens
Resources: Aquaponics Supplies