Not sure which substrate is ideal for your plants? We know that different plants have different requirements, but you must also consider your personal preferences. Taking that into account, we have created a variety of substrates to meet your needs. Let’s go through the traits, similarities, and distinctions of our substrates, so you can determine which one is the best suit for you.
Similarities and Differences
First things first, all our substrates have one thing in common: they’re all high quality. We search for quality raw materials from reliable sources and carefully manufacture our substrates. We conduct rigorous tests to ensure safety and quality, so you can trust that our products meet our high standards.
When we talk about differences in substrates, these generally lie in 3 aspects: type of growing medium, composition of the substrate and level of fertilization.
Â
Growing medium
In terms of growing medium, we can consider that a substrate can be found in a range from inert to active growing media.
The difference between these two terms lies in their ability to interact with matter and store nutrients:
The active substrates provide support for the plant and act as a reservoir for the nutrients given by fertilization, storing or releasing them as needed by the plant.
The inert substrates just serve as a support for the plant and do not participate in the nutrient adsorption and fixation process. As a result, nutrients must be given by the fertilizer solution.
But there are also substrates with an intermediate reactivity, so can’t be completely enclosed in one or in another.
Peat, for example, is a clear case of a reactive substrate. Peat substrates interact and store the nutrients we offer, having a certain buffering action on the pH. On the other hand, clay pebbles or rockwool do not retain nutrients. There are some substrates, such as coconut fiber, that are not as reactive as peat, but also are not completely inert as there is some exchange and retention of nutrients in them.
What does all this mean? Well, depending on the way you grow, and your experience, some substrates may be easier and more resilient to work with than others.
Â
Composition of the substrate
On the other hand, and in relation to the growing medium, there is the composition of the substrate. Depending on the different materials that it is composed of the substrate will have different characteristics. This usually means differences in the substrate air percentage and water management, i.e., its drainage or water retention capacity.
Substrates with different compositions and properties from left to right: Cocos Substrate, Kilomix, Hydro Rokz 60-40.
Higher porosity leads to a better aeration, and a high aeration means more oxygen is available to the root environment. Usually, the substrates achieve this increased aeration with the addition of materials such as perlite, clay pebbles, larger coco chips and longer and more rigid fibres. Bigger particles help improve the percentage of air in the substrate by adding structure and thereby create empty pockets. The empty pockets will fill with water, when watering, but drained completely afterwards.
This sounds great, right? And it is! But consider that the higher the percentage of air in a substrate, the less water holding capacity it has So, watering will have to be more frequent, this applies especially for large plants, which will use up this water reserve really fast.
So, if you have plants that require constant moisture at the roots, you water by hand, or you live in a very hot place, you may consider choosing a substrate that is not as airy and retains moisture better. The trick to know if a substrate is aerated or not is to check the % of air in the bag. Highly aerated substrates will have â‹ť25% of air, medium aerated substrates between 15 and 25 %.
Having less than 15% of air won’t necessarily be bad but the plant growth will be slower. This is mostly because the substrate contains less oxygen overall.
Â
Level of fertilization
This aspect has more to do with the preferences of the hobbyist. But usually for germinating seeds, transplanting seedlings and for plants that can easily suffer from over-fertilisation, it may be appropriate to choose substrates with a low to medium level of fertilization. Substrates without low fertilization, or with low fertilization, have the advantage of allowing the desired nutrition regime to be started from the beginning.
Peat substrates
Let’s take a closer look at our peat substrates. Peat is a resilient and forgiving substrate that is perfect for beginners. All Atami peat substrates are made from a balanced and high-quality peat mix, and the differences lie in the fertilization or extra compounds of each product.
Janeco-Light-Mix is a lightly fertilized substrate with a 10% perlite mixed in. This substrate is perfect for “difficult” plants, which won’t become over-fertilized quickly due to its light dose of fertilizer. It is also ideal for germinating seeds and seedlings. As its name “Light – Mix” suggests, the added perlite makes the substrate airy and improves water drainage. There is sufficient nutrition available for the early development of the plant, just be sure to add any fertilizer after the first/second week for optimal results.
If you are looking for an aerated substrate like Janeco-Light-Mix but heavily fertilised, try Kilomix. This substrate contains a mixture of mineral and organic fertilisers. The mineral fertiliser can be absorbed by the plant immediately. Supported by the organic fertilisers, which provide a constant supply of nutrients over a longer period, we get an ideal combination to nourish the development of the plants.
The Bi Grow Mix substrate combines the best of both worlds with a mixture of peat and coco coir. This substrate is forgiving due to the combination of properties, making it easier to deal with minor errors. When it comes to the fertilization level, we can consider it medium; in between Janeco-Light-Mix and Kilomix. The plants can root on it directly from the initial stage and then develop further in size.
Coco-based substrates
Moving on to our coco substrates, we use only the highest quality coco coir that undergoes rigorous processing and testing before reaching you. This includes aging, washing, and buffering of the coco fibres; the latter step being the most important one for a good quality coco substrate. A poorly buffered substrate will capture the nutrients you give your plants, so it is crucial to choose a substrate that has been correctly buffered. Once you have a high-quality coco substrate, this medium is for the beginner-medium hobbyist because the nutrition must be tailored to it.
Cocos Substrate offers 100% natural coco coir that has been washed, matured, and buffered. This substrate is lightly fertilized and has excellent water retention. It’s a light and airy substrate that allows oxygen to reach the roots and leads to a healthy and well-developed root system.
If you’re looking for something with even more aeration, try our High Porosity Cocos substrate. This substrate offers all the benefits of growing with our high-quality coco coir, with the added benefit of aeration provided by perlite. This substrate has an air percentage of about 30%, which allows the production of more root hairs and enables plants to absorb more nutrients.
For hydroponic growing, we recommend our Hydro Rokz Cocos 60-40 substrate. This substrate features a balanced blend of clay pebbles and coco fiber. Hydro Rokz Cocos 60-40 offers many benefits for hydroponic growth: the clay pebbles ensure excellent drainage as they retain almost no water, while the coco substrate increases the water retention of the substrate. The added coco substrate keeps the moisture in the root zone at stable levels between waterings. This balanced substrate supports healthy root growth and nutrient intake.
Inert substrate
If growing hydroponically, we cannot forget about clay pebbles, which are chemically inert, pH neutral and retain hardly any water or nutrients. This means that you can adjust the pH, EC and choose the nutrient solution from the start. This medium normally needs greater skill, as plants will bear the impact of even the smallest mistakes.
Inside of this category we have Hydro Rokz. This substrate is ideal for passive hydroponic applications and active hydroponics systems, using it as a growing medium, often in combination with an oxygen pump. Also, Hydro Rokz can be placed at the bottom of the pot when growing on another substrate, or mixed in with other substrate, to make the growing medium more aerated.
Hydro Rokz is free of pathogens and is not of organic origin, which means that root diseases also have less grip on your crop. Less disease in the substrate means healthier plants.
Frequently Asked Questions About Choosing the Right Growing Substrate for Your Plants
What is a growing substrate and why does it matter in cultivation?
A growing substrate is the medium in which plants root and develop. Choosing the right substrate matters because it affects nutrient retention, water-holding capacity, aeration, and overall plant health. The article explains that some substrates are “inert” (support only) while others are “active” (store and release nutrients).
What does “active” vs “inert” substrate mean and how does it impact my grow?
An “active” substrate (like peat) interacts with nutrients; it can buffer pH and store minerals. An “inert” substrate (like clay pebbles) doesn’t retain nutrients, so all feeding must come externally. This distinction influences how you manage fertilisation and plant nutrition.
How do compostion and aeration of a substrate affect plant root development?
The composition (like perlite content, fibre size, particle structure) determines how much air and water the root zone receives. High-porosity substrates drain quickly and provide more oxygen, but hold less water. A key trade-off for root health.
What should I consider regarding the fertilisation level of a substrate when selecting one?
Substrates come with varying fertiliser levels. Low, medium or high. For seedlings or plants sensitive to over-fertilisation, choose a low-fertiliser substrate. For heavy feeders, a richly fertilised substrate may simplify feeding.
For beginners, which substrate types are most forgiving and why?
According to the guide, peat-based substrates (e.g., a lightly fertilised peat mix) are the most forgiving. They buffer small mistakes, making them ideal for beginners.
What are some example product types mentioned, and what growing styles do they suit?
Examples include:
- “Janeco-Light-Mix” (peat + perlite, low fertiliser) for seedlings and delicate plants.
- “Kilomix” (peat + perlite, high fertiliser) for experienced growers with heavy-feeding plants.
- “Cocos Substrate” (100% washed & buffered coco coir) for growers wanting high drainage, aeration and using tailored nutrient regimes.
If I’m growing hydroponically, which substrate type should I look at?
For hydroponic setups, inert or minimally interactive substrates like clay pebbles (e.g., Hydro Rokz) or mixes with coco + pebbles provide excellent drainage and let you fully control nutrients and pH.
How do I evaluate the aeration percentage of a substrate and why is it important?
The article states aeration is often given as “% air” in the bag. More than ~25% means high aeration (less water retention). If aeration is under ~15%, growth may be slower due to less oxygen. Knowing this helps you match substrate to plant and watering rhythm.
What are the main user pain-points when choosing a substrate and how does the article address them?
Major pain-points: selecting between substrate types, dealing with over/under-watering, matching nutrient regime, and managing mistakes. The article addresses them by breaking down how to assess substrate (medium type, composition, fertilisation level) and giving examples matched to grower experience.
What is the takeaway advice for selecting the right substrate for your plants?
Once you understand your plant’s needs and your own growing style (seedlings, heavy feeders, hydro setup, beginner vs advanced), there’s a substrate to match. Choose based on: medium type (peat/coco/inert), composition (aeration vs water retention) and fertilisation level. That ensures optimal root development and plant performance.
Conclusion
In short, once you know your preferences and the growing needs of your plants, there is a substrate that can best suit you. Whether you need a more aerated substrate, a completely inert one, or choose according to the level of fertilization, we’ve got you covered. And, of course, you can be sure that all of our substrates have been carefully produced and tested to ensure the best results. Atami substrates… for plants that are happy from the roots up!
