Does Aquaponics Use Soil? (What You Should Know)

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Over the decades, many new aquaponics enthusiasts have successfully built small scale and commercial aquaponics systems that produce higher plant yield as compared to conventional planting. However, some traditional growers who are used to geoponics or cultivating plants in soil are still in disbelief that it is possible to grow crops using only water and fish waste. Despite many studies about aquaponics that explains how the system works, some are still asking: does aquaponics use soil as grow media to facilitate more nutrient uptake? How does this work exactly?

There is no doubt that soil supplies necessary nutrients for plant growth in traditional gardening. However, in an aquaponics system, the plants receive nutrients from the fish waste, which completely eliminates the need for soil. Nevertheless, it is necessary to note that some aquaponics growers are now experimenting with soil as grow media for their systems.

In this article, we will discuss how plants grow in a soilless aquaponics system and what should be considered when embarking on this type of gardening. We will also feature some systems that use soil as grow media even though there are many available soilless substrates in the market.

How does a soilless aquaponics system work

The aquaponics system creates a symbiotic relationship wherein the fish produces nutrients for the plants, and in return, the water is filtered and reused by the fish. This is similar to most freshwater ecosystems like ponds and lakes. To understand how this type of gardening operates without the soil, here are the three primary elements needed:

Plants

The very reason why growers set up an aquaponics system is to grow plants more sustainably. Despite receiving much of the benefits from the system, the plants also play a vital role in maintaining a balanced unit. They serve as a natural filter by absorbing nitrates from the fish waste or detoxifying the water for recirculation without causing fish stress.

Fish

Fish that live in the tank make up for the aquaculture component an aquaponics system, giving much of the nutrients needed by the plants through the waste they produce. This is why nutrient supply isn’t a problem in aquaponics systems despite the absence of soil. The fish produces enough waste in the form of ammonia, which is later converted into useable nutrients.

Bacteria

Without bacteria, it’s next to impossible to grow both plants and fish in an aquaponics system. Since the fish excretes waste in the form of ammonia, a highly toxic substance, the bacteria would have to convert them into nitrates. This will then serve as the source of plant nutrients. This process of converting ammonia into nitrates is called the nitrification process, and this usually happens through the aid of a biofilter.

Things to consider in soilless aquaponics planting

The absence of soil in an aquaponics garden causes a lot of confusion to many traditional growers. The question of ” does aquaponics use soil?” arises, especially in plant support and nutrient supply. To answer this, some considerations in aquaponics planting are discussed below.

Plant support

Using grow media is very common in aquaponics gardening, especially for small scale units. Soilless aggregates are used to support the plants by establishing a strong root structure. Some common grow media are expanded clay, rock, gravel, Rockwool, pine bark, and vermiculite, which can easily be purchased from local and online aquaponic stores. In addition to providing stability to plants, these grow medium also allows nutrient absorption.

Nutrients

In traditional gardening, significant nutrients such as nitrogen, phosphorus, and potassium come from the soil. Since aquaponics doesn’t employ the use of soil, most of the nutrients that the plants need come from the fish waste that is converted by bacteria into nitrates. In cases where plant deficiencies occur, organic fertilizers such as bone meal and banana peels are used as supplementary nutrient sources. 

Using soil as grow media

Despite being a fundamentally soilless gardening system, some aquaponics growers experimented on using soil as grow media for their plants. The Pettengill Farm in Salisbury, Massachusetts and Growing Power in Milwaukee, Wisconsin are some of the aquaponics farms that use soil as grow media mentioned in an article written by Kailey Burke, a scholar of sustainable food and farming. Burke stresses that using soil gives thermal mass and promotes temperature stabilization in an aquaponics system.

Another farm that uses soil as an aquaponics grow media is the Sahib Aquaponics Research Farm located at Winterpark, Florida. The soil used in their aquaponics garden is made of coir, peat humus, and pine bark compost.

Conclusion

The question “does aquaponics use soil?” should not confuse traditional growers because the name of the system itself implies the use of water as the primary means of plant growth. It works through a recirculating system made possible by three key elements: plant, fish, and bacteria. 

In terms of plant support, some aquaponics enthusiasts opt to experiment with soil as their grow media. However, there are limited studies that prove its effectiveness, so it would still be better to use soilless aggregates to provide stability to aquaponic plants. For the growers who are more concerned that the plants might develop nutrient deficiencies, organic fertilizers can be supplementary to the nitrates produced from fish waste.