Creating an optimal hydroponic growing medium often requires combining different substrates to achieve a balance of water retention, aeration, and nutrient availability. This article examines the potential benefits of using perlite, expanded clay granules, and coir in two-component mixtures for hydroponic systems and discusses the factors to consider when determining the ideal ratio for specific applications.

Two-Component Growing Media Mixtures

Perlite and Coir:

Perlite is a lightweight, porous material with excellent water retention and capillary action, while coir is a natural fibre extracted from coconut husks that offer both water retention and aeration. Combining these two substrates can result in a more balanced growing medium with the following advantages:

  1. Improved water retention and drainage: Mixing perlite and coir can provide a balance between water retention and drainage, ensuring optimal moisture levels for plant growth.
  2. Enhanced aeration: The combination of perlite and coir can increase the air spaces within the growing medium, promoting healthy root development and preventing root rot.
  3. Increased nutrient availability: Coir has a natural cation exchange capacity, which can improve nutrient availability in the growing medium.

Expanded Clay Granules and Coir:

Expanded clay granules are lightweight, porous, and provide good aeration, while coir offers water retention and aeration. Combining these two substrates can result in a balanced growing medium with the following benefits:

  1. Balanced water retention and drainage: The mixture of expanded clay granules and coir can achieve a desirable balance of water retention and drainage.
  2. Improved aeration: Both expanded clay granules and coir provide adequate aeration for plant roots. Mixing the two can further optimize air spaces within the growing medium.
  3. Enhanced nutrient availability: Like perlite and coir, the combination of expanded clay granules and coir can improve nutrient availability through coir's cation exchange capacity.

Factors to Consider When Determining the Ideal Mixture

  1. Plant requirements: Different plant species have specific water, aeration, and nutrient requirements. The ideal ratio of the two substrates will depend on the specific needs of the plants being grown.
  2. Hydroponic system type: The type of hydroponic system may influence the optimal ratio of growing media. Some systems require faster drainage, while others may benefit from increased water retention.
  3. Environmental factors: Local environmental conditions, such as temperature and humidity, can affect water retention and evaporation rates. Adjusting the ratio of the substrates can help maintain optimal moisture levels in the growing medium.

Potential Ratios and Their Applications

It is essential to experiment with different ratios of the selected substrates to determine the most effective mixture for specific plants and hydroponic systems. Here are some potential combinations to consider:

  1. 50% Perlite / 50% Coir: This balanced mixture provides adequate water retention and aeration, making it suitable for a wide range of plants and hydroponic systems.
  2. 70% Expanded Clay Granules / 30% Coir: This ratio offers better drainage and increased aeration, suitable for plants that are sensitive to overwatering or in hydroponic systems that require faster drainage.
  3. 40% Perlite / 60% Expanded Clay Granules: This combination provides moderate water retention and improved aeration, ideal for plants with moderate moisture requirements or in environments with high evaporation rates.

Benefits and Challenges of Combining Substrates in Hydroponics

  1. Improved aeration and water retention: By combining substrates with different characteristics, such as coir for water retention and perlite or expanded clay granules for aeration, the mixture can provide an ideal balance for plant root growth and development.

  2. Nutrient availability: Coir has a natural ability to hold onto nutrients, making them available to plants over time. Combining it with other media can help maintain a consistent nutrient supply and prevent nutrient leaching.

  3. Enhanced root support: A mixed substrate can provide better structural support for root growth, preventing compaction and allowing for proper gas exchange and water movement through the growing medium.

  4. Flexibility and customization: Growers can adjust the ratio of different substrates to create a tailored growing medium for specific plant species or hydroponic systems.


  1. Inconsistency: The physical properties of different substrates can vary, potentially leading to an uneven distribution of water, air, and nutrients throughout the growing medium.

  2. Degradation: Some substrates, like coir, can break down over time, which may cause changes in the physical properties of the growing medium, affecting plant growth and system performance.

  3. Compatibility: Not all substrates are compatible with every hydroponic system. Growers must choose the right combination of materials for their specific system to ensure optimal plant growth.

  4. Cost: Combining different substrates may increase the overall cost of the growing medium, especially when using high-quality materials or large quantities.

  5. Maintenance: Mixed substrates may require additional monitoring and maintenance to ensure proper nutrient and pH levels, as well as regular cleaning and replacement to maintain optimal growing conditions.

In conclusion, combining substrates like perlite, expanded clay granules, and coir in two-component mixtures can offer significant benefits for hydroponic systems. These mixtures can provide improved aeration, water retention, nutrient availability, and root support, and allow for flexibility and customization according to the specific needs of various plant species and hydroponic systems. However, there are also challenges to consider, such as inconsistency, degradation, compatibility, cost, and maintenance. By carefully considering these factors and experimenting with different ratios, growers can optimize the combination of substrates to achieve a balanced growing medium that supports healthy and productive plant growth in their hydroponic systems. This tailored approach allows for successful adaptation to individual circumstances and helps ensure optimal conditions for plant growth and development


Coir, derived from the mesocarp tissue of the coconut (Cocos nucifera) fruit, has gained attention as a viable alternative to peat moss in hydroponic systems. This article examines the properties of coir and its potential applications in hydroponic cultivation.

Physical Characteristics

Coir dust, the fine fraction of coir, is a lightweight material with a bulk density of 0.04-0.08 g cm-3 (Evans et al., 1996). Its total porosity ranges between 86-94%, while its air-filled porosity is 9-14% (Lemaire et al., 1998). Coir fiber, the coarse fraction, has distinct characteristics, such as a total porosity of around 98% and an air-filled porosity of around 70% (Lemaire et al., 1998). Coir dust has a relatively high water-holding capacity of 35% (Prasad, 1997), resulting in superior growth of foliage plants compared to peat (Stamps & Evans, 1997). The high unsaturated hydraulic conductivity of coir leads to improved water availability and better yield of roses compared to UC mix (Raviv et al., 2001).

Chemical Characteristics

Crude coir contains high levels of sodium and chloride, which may harm plants. During the production process, coir must be washed, and calcium and magnesium are typically added to facilitate sodium removal and provide nutrients (Prasad, 1997). Coir is rich in phosphorus and potassium, which should be considered in fertilization programs. The cation exchange capacity ranges from 320 to 950 mmolc kg-1, and the carbon-to-nitrogen (C/N) ratio averages around 117 (Noguera et al., 2000; Evans et al., 1996). Nitrogen immobilization may occur in coir dust but not in coir-based media with conventional fertilization programs (Handreck, 1993b; Noguera et al., 2000).

Hydroponic Applications

Coir can serve as a standalone medium or as an ingredient in a mix for hydroponic cultivation of vegetables, cut flowers, potted plants, tree saplings, and young foliage plants (Meerow, 1994; Evans & Iles, 1997). Coir has shown growth results comparable to peat moss and is widely accepted as a peat substitute (Meerow, 1994; Evans & Iles, 1997). Furthermore, coir can serve as a rooting medium for cuttings under mist or in high humidity chambers (Lokesha et al., 1988).


Coir has several properties that make it a promising alternative to peat moss in hydroponic systems. With careful consideration of its physical and chemical properties, coir can be utilized as an effective growth medium for various plant species.


  1. Evans, M. R., Stamps, R. H., & Lemaire, F. (1996). Physical and chemical properties of coir dust. HortScience, 31(6), .
  2. Lemaire, F., Stamps, R. H., & Evans, M. R. (1998). Coir fiber as an alternative to peat in media for tomato greenhouse production. HortScience, 33(6),
  3. Meerow, A. W. (1994). Growth of two subtropical ornamentals using coir dust (coconut mesocarp pith)

In the summer of 2009/10, a severe heatwave hit South-East Queensland, shutting down the Ghost Gully Produce farm in Gatton for five weeks. Farm losses are, of course, costly in terms of lost product and production, and potential lost customers. Temperatures of up to 45°C were being routinely reached. Overhead sprays were used to cool the systems, but were blown over the systems by westerly winds.

We were desperate to cool the systems, but the best cooling towers were only capable of reducing temperatures by 4–6°C. Their effectiveness, pricing and running costs made us wonder if there could be a better way.

Gatton is not only prone to extreme summer temperatures, but also to sub-zero winter temperatures. What was needed was a solution to thermal dormancy (and worse!) in summer, and growth shut down in winter.

I stumbled across heat pumps with underground piped heating used in European homes to maintain an even temperature through summer and winter—could that work here? I tried to research ground temperatures, but data was difficult to come by. A customer knew of a farmer who had trialled a similar installation, but only achieved limited success. The idea was clearly not new, but if we could make it work well, it would be a solution for summer and winter, with reduced overheads compared to other heating and cooling methods. Still, we were flying into this blind.

Kelp Fulvic Plus: A Comprehensive Analysis of its Benefits for Commercial Farming

Abstract The use of seaweed extracts as a source of nutrients and growth promoters for crops has been widely studied and well documented. In this paper, we will examine the benefits of Kelp Fulvic Plus, a nutrient additive that contains a combination of seaweed extracts, fulvic acid, phosphorus, potassium, and silicate. Our research aims to provide a comprehensive overview of the benefits of Kelp Fulvic Plus and the underlying mechanisms behind these benefits.

Introduction Seaweed extracts have been widely used in commercial farming as a natural source of nutrients and growth promoters for crops. They contain a variety of compounds, including hormones, minerals, and other essential nutrients that are beneficial for plant growth and health. Kelp Fulvic Plus is a nutrient additive that contains a combination of seaweed extracts, fulvic acid, phosphorus, potassium, and silicate. The seaweeds used in Kelp Fulvic Plus include Bull Kelp from South Australia and Tasmania, as well as Sargassum, Ascophyllum nodosum, and Laminaria.

Benefits of Kelp Fulvic Plus
  1. Improved Plant Growth and Yield: Seaweed extracts have been shown to improve growth and yield in a range of crops. This has been attributed to the presence of growth hormones, minerals, and other essential nutrients in seaweed extracts. Kelp Fulvic Plus is no exception, as it contains all these beneficial compounds that can help improve plant growth and yield.

  2. Enhanced Nutrient Uptake: The presence of growth hormones, chelating agents, and other compounds in Kelp Fulvic Plus can help improve nutrient uptake by plants, leading to increased growth and health. This is important in commercial farming where the plants need to be healthy and productive in order to maximize yields.

  3. Improved Stress Tolerance: Seaweed extracts have been shown to help plants better cope with stress factors such as high salinity, drought, and extreme temperatures. Kelp Fulvic Plus contains seaweed extracts that can provide similar benefits, helping plants better handle environmental stress and maintain healthy growth.

  4. Increased Disease Resistance: Some studies have suggested that seaweed extracts can improve plant resistance to disease by strengthening the plant's immune system. Kelp Fulvic Plus contains seaweed extracts that can provide similar benefits, helping to protect plants from disease and increase overall plant health.

  5. Better Root Development: Seaweed extracts have been shown to help improve root development, leading to stronger and healthier plants. Kelp Fulvic Plus contains seaweed extracts and other beneficial compounds that can help improve root development and provide a strong foundation for healthy plant growth.

Conclusion In conclusion, Kelp Fulvic Plus is a highly beneficial nutrient additive for commercial farming. It contains a combination of seaweed extracts, fulvic acid, phosphorus, potassium, and silicate that provide a range of benefits for plant growth and health. With its ability to improve plant growth, increase nutrient uptake, enhance stress tolerance, increase disease resistance, and improve root development, Kelp Fulvic Plus is an excellent choice for commercial farmers looking to maximize yields and improve plant health.

  1. Rizwan, S. T., Iqbal, A., & Shafiq, M. (2017). Influence of seaweed extracts on growth, yield and quality of crops. Journal of Plant Interactions
  2. Beissner, K., & Strzelczyk, E. (2011). The role of silicate in higher plants. New Phytologist
  3. Omar AliAdesh RamsubhagJayaraj Jayaraman (2020) Biostimulant Properties of Seaweed Extracts in Plants: Implications towards Sustainable Crop Production



Click through to view a Practical Hydroponics article explaining the application of farm automation and ozone at Ghost Gully Produce, Gatton.

Ghost Gully