Dragon Stones with Soil © stock.adobe.com ID: 270140126 | coffmancmu
Soil enjoys steady popularity especially in tetra tanks and in the area aquascape.
It is an active substrate and its components ensure a supply of nutrients, which plants gratefully reward with good growth.
This article shows the origin, the components and the possible uses of soil.
What is meant by «soil»?
Soil is an English word and literally translated means nothing more than ground or earth. But among aquarists, soil means something else:
In contrast to aquarium gravel and sand, soil refers to an active substrate that can change the water properties. It is mainly used by experienced aquarists and especially by aquascapers to design their underwater landscapes.
No wonder, because the initiator of aquascaping, the Japanese Takashi Amano, also put together the first soil as a substrate especially for his natural aquariums. In the meantime, the Japanese company ADA, which he founded, offers a whole range of soils with different compositions for different types of aquariums and areas of application under the Aqua Soil brand.
However, the special mixture of different components of the soil remains a company secret. Other companies are now also offering such active soil mixtures, for which the term soil has generally become established.
What are the components of soil?
The basic substance used is volcanic earth, which is rich in minerals and other trace elements and plant nutrients. These earth particles are pressed into a spherical shape and burned.
Activated carbon is sometimes added to this active substrate, which adsorbs dirt and other particles and thus ensures particularly clear water free of turbidity. A clean and easy-to-use method to save yourself filtering through peat or the black water additives available in specialist shops.
The volcanic earth used for the soil also contains numerous humic substances and fulvic acids, which acidify the water well and keep it free of cloudy bacteria with their slightly bactericidal effect.
How is soil made?
The volcanic earth is mixed with carbon powder, sometimes also with other additives, using special methods and pressed into certain grain sizes and then burned into spherical shapes. The resulting soil balls look similar to the baked expanded clay balls used in hydroponic plants.
In contrast to soil, however, this expanded clay does not contain any nutrients, so that liquid fertilizer must also be added in hydroponics. In contrast, the soil balls already contain all trace elements and nutrients for the plants.
Soil balls are just as dimensionally stable as the expanded clay balls used in hydroponics, but they are more elastic and softer. This makes it easier for the aquarium plants to root and anchor in the soil substrate.
On the other hand, the haptic between the individual soil balls is so good that, if they are slightly moistened, you can model dune-like landscapes, slopes and hills that do not collapse or melt again under water like with pure aquarium sand or fine gravel.
That is why soil is very popular as a substrate, especially in aquascaping.
What properties does soil develop in aquarium water?
- The soil balls act as ion exchangers in the water. They remove carbonates and other cations from the aquarium water and release hydrogen ions (H+) to compensate. As a result, the water becomes more acidic and the pH drops.
- Soil also removes calcium and magnesium ions from the water, i.e. the two cations that determine the total hardness (GH) of the water. As a result, the water consequently becomes softer.
- The hydrogen ions (H+) released by Soil in the water combine with the hydrogen carbonate ions dissolved in the water to form carbonic acid, which in turn then dissociates into water and carbon dioxide depending on the pH value. This also reduces the carbonate hardness (KH).
Conclusion: Soil as substrate can lower the pH value, the total and carbonate hardness. The water becomes more acidic and softer.
In addition, the soil releases well-buffered humic substances into the water, which means that the aquarium water can take on a slightly amber-like to brownish colour. These are exactly the environmental factors that many of our ornamental fish, which come from the running waters of tropical rain forests, need.
Soil has also stored essential nutrients for the aquatic plants, which are gradually released into the water and can be absorbed by the plants rooted between the soil balls.
However, this effect is usually somewhat overestimated in aquaristics. Because many aquatic plants do not absorb these nutrients through their roots, but through their leaf surfaces. This applies above all to stem plants with finely feathered and divided leaves.
How long does the effect of the soil last?
The influence of the soil on the water in its capacity as a cation exchanger does not last forever. This effect only lasts for a few years. Of course, the concentration of the nutrients contained in the soil also decreases over time and the fertilizer effect on the plants noticeably decreases.
Then the aquarium water must be supplied with nutrients by other additives and an organic long-term fertilizer must be added to the soil or the soil must be replaced.
However, this also means that the most important water parameters such as pH value, total and carbonate hardness, as well as the concentrations of nitrate, iron and phosphate dissolved in the water must be measured at regular intervals.
In addition, the specialist trade offers inexpensive and easy-to-use sets with up to 14 different water tests.
For which aquariums is Soil particularly suitable?
Soil is particularly popular in aquascaping, as it is better for modeling impressive underwater landscapes than with pure aquarium sand or gravel.
However, since the effect of the soil as a cation exchanger and nutrient supplier decreases over time and then countermeasures have to be taken to keep the environmental conditions in the aquarium stable, using it as an active substrate requires a sure instinct and some experience in aquaristics.
An inactive substrate – aquarium sand or fine gravel – should therefore be used for the first aquarium you set up yourself.