Aquarium

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Published: 2014-08-20, Updated: 2017-01-16

Experiments: Analysis of aquarium substrates

2019 Comment

I consider the substrate to be the most important building element of the planted aquarium. It follows logically that to know its exact composition is crucial if the aquarist wants to systematically achieve success. Unfortunately, from today's point of view, I do not find the below analyzes so useful anymore, because they are far from finding everything I consider important today. A much better way to find out the ideal substrate composition seems to me what my colleague Maq was doing in his experiment called Michurin's vacation 2018 (unfortunately available only in Czech). Hopefully he will find out what substrate components are important for good plant growth.

In this article you'll find the laboratory analyses of selected aquarium substrates.

Evaluation of the results of soil analyses

See Regulation no. 275/1998 in Czech Collection of LawsMinistry of Agriculture Decree on agrochemical testing of agricultural soils and determining the forest soil properties

Content of particles (grains) < 0,01 mm in %
Type of soilDesignationGraininess I. (%)
LightSand<10
Loamy sand10-20
MediumSandy loam20-30
Loam30-45
HeavyClay loam45-60
Silty clay60-75
Clay>75
pH (soil exchange reaction):
pHrating
<4.5extremely acidic
4.5-5.0strongly acidic
5.1-5.5acidic
5.6-6.5slightly acidic
6.6-7.2neutral
7.3-7.7alkaline
>7.7strongly alkaline
Oxidizable carbon and humus:
Cox (%)Humus (%)content
<0.6<1.0very low
0.6-1.11.0-2.0low
1.2-1.72.1-3.0medium
1.8-2.93.1-5.0high
>2.9>5.0very high
Sorption properties (CEC):
CEC (mM/100g)designation
>30very high
30-25high
24-18upper middle
17-13lower middle
12-8low
<8very low

Available nutrients (mg/kg):
ContentPKCaMg
soilsoilsoil
lightmediumheavylightmediumheavylightmediumheavy
low<50<100<105<170<1000<1100<1700<80<105<120
satisfactory51-80101-160106-170171-2601001-18001101-20001701-300081-135106-160121-220
good81-115161-275171-310261-3501801-28002001-33003001-4200136-200161-265221-330
high116-185276-380311-420351-5102801-37003301-54004201-6600201-285266-330331-460
very high>185>380>420>510>3700>5400>6600>285>330>460
 
Carbonate content:
carbonates %content
0none
0.1-0.5low
0.6-3.0medium
3.1-5.0high
>5.0very high
Mineral nitrogen:
mg/kgcontent
<5very low
5-15low
15-30medium
30-45good
>45high

The content of iron (Fe) in the topsoil is usually in the range from 5 to 50 g/kg (usually present as an insoluble Fe oxides or Fe phosphates).
The content of manganese (Mn) in the topsoil is usually in the range from 20 to 3000 mg/kg (most of the available Mn is bound in organic complexes).

The nutrients in the soil are either in form of the soil solution (in ionic form), or in the solid phase in the bonds: as salts adsorbed, or exchangeably bound on the surface of mineral and organic sorbents, fixed in clay minerals, bound in the organic matter, in the biomass, in the crystal lattice of silicates. Total nutrient content in soil is relatively high and different at various soils. Available nutrients make up only a small portion of the total nutrient content in the soil and contain only a few tenths up to 1% of all content. This small proportion is mainly made by nutrients dissolved in the soil solution, by nutrients bound in the soil complex (CEC), and by nutrients bound in the soil in compounds that are soluble in weak acids (H2CO3) or bases (NaHCO3). Receivable nutrients are characterized as a proportion (part) of the available nutrients, which is determined by their solubility in water (or more precisely in the soil solution), but also by the conditions of their uptake and uptake capabilities of plants. The remaining 99 percent or more of all nutrients in the soil is bound more or less firmly in the mineral, organic-mineral, and organic fraction of the soil, and forms a "reserve" (buffer) of nutrients for plants. The degree of making this reserve available to the state accessible to plants depends on environmental pH, particle size and strength of their crystal lattice, the position of ions inside and around the lattice of crystals, course of mineralization, and the like. A nutritional regimen of soils depends on the character of sorption (clay, humus) microbial and makrobial activity in the soil, pH, ratio of water and air in the soil, content of macro- and micronutrients, and on the degree of degradation of organic matter in the soil. The nutrients bound by ion-exchange to soil colloids, especially the humic ones, may ensure an optimum state of nutrients in the soil solution in a sufficient and continuous flow.
– Prof. MSc. Rostislav Richter, MD.

Analyzes results

  ADA Aqua Soil Amazonia

Producer: ADA Aqua Design Amano

Marketing description of the substrate:

Amazonia is a substrate material rich in organic acids and nutrients, which promotes the growth of rooted plants. In combination with the storage substrate Power Sand is Aqua Soil an ideal substrate for plants. Finer Powder type is used for smaller tanks or as a top layer posited over a normal type of Amazonia substrate. This product is designed for growth and support of aquatic plants and tropical fish in the aquarium. Unlike some soil substrates in the market, which prevent an increase in hardness by means of chemical treatment, Aqua Soil reduces the water hardness in a natural way, thus creating a slightly acidic environment which most aquatic plants prefer. Aqua Soil has excellent shape and density, so the root system of plants develops better in it than in the sea sands or other soil substrates. This heat-treated natural soil substrate is a completely new kind of substrate. Aqua Soil produced from natural soils and containing a high proportion of organic nutrition creates a "microcosm" or "live substrate" in cooperation with supporting additives, that supports the activity of microorganisms. In combination with an underlying Power Sand substrate (sold separately) improves a rapid colonization of the substrate by bacteria, and creates an ideal environment for rooted plants.

Recommended usage:

Do not use this product in conjunction with other manufacturers (excessive supply of nutrients could result in turbid water or algae infestation). Do not use any preparations for treating fish diseases together with this product. Flushing the substrate before the first use is not necessary because it could consequently lead to fragmentation of granules and water turbidity. 9ℓ packaging is the standard amount suitable for setting up an 24" (60 cm) aquarium (thickness of the substrate in this case will be 4 cm). After filling the aquarium with water the water will be cloudy for a while. Turbidity can be removed either immediately through the water changes, or gradually through filtration. This substrate contains pebbles and plant parts, which are materials commonly found in each soil. Do not use undergravel filter together with this product. For the cultivation of aquatic plants we recommend using an external canister filter. Because this product naturally acidify the water and reduces its hardness, it is not suitable for tropical fish that prefer alkaline water. This product is also not suitable for fish that dig the bottom. When using the Amazonia substrate an organic substances (humic acids) can leach into water, causing a yellow or brown coloration if the local tap water has a high pH. Discoloration of water disappears when the aquatic plants expand and cover the entire substrate. Until the plants fully proliferate, do frequent water changes, and use an activated carbon as an optional filter medium as well. The filter output should not be aimed directly into the substrate to whirl it. Filter input should not be close to the substrate, so that the substrate particles are not sucked into the filter.

Characteristics of the analyzed substrate:
Trade nameAqua Soil Amazonia [New]
Package9ℓ
Graininess4-5 mm
Weight0.73 kg/ℓ
Country of purchase Bulgaria [Georgi Chaushev]
Statenew, never used
Date of purchase: 07/2012
Date of analysis: 08/2014
Results of the laboratory analysis:
ParameterValueUnitNote
pH4.62strongly acidic reaction
carbonates [CO3]0.2 %low content
N-total3,850   mg/kgsum of all forms of inorganically and organically bound nitrogen (ammonia, nitrite, nitrate and organic nitrogen)
98-99% of the nitrogen in the soil is in the organic form, and only a small part is in the mineral form.
Nitrogen bound in the organic form presents a stock form of N that plants can use only after mineralization.
N-NH4+ mineraln/amg/kg
N-NO3- mineraln/amg/kg
P-available<2   mg/kglow content
K-available66   mg/kglow content
Ca-available348   mg/kglow content
Mg-available36   mg/kglow content
Fe-total34,100   mg/kg(average content)
Mn-totaln/amg/kg
CEC26.88mM/100ghigh cation exchange capacity
Exchangeable H+35.3 mM/100ghydrogen that is in the sorption complex
Cox4.29%very high content (total oxidizable organic carbon)
humusn/a%very high content (stable organic component of substrate)
Clay [Graininess I]15.6 %→ light, loamy sand soil
Silt [Graininess II]24.7 %
Sand [Graininess III]59.7 %
ADA Aqua Soil Amazonia substrate belongs to the category of light, loamy sand soils (clay content = 15%) with high content of organic carbon (4%), and high sorption capacity (CEC = 27 mM/100g). It has a strongly acidic reaction (pH 4.6), and contains a very high amount of exchangeable hydrogen (35 mM/100g). The content of available nutrients (phosphorus, potassium, calcium and magnesium) is low. The iron content is average (34 g/kg) and corresponds to the values common in most soils.

Calculation of the substrate saturation

CEC = "Potential" sorption capacity (i.e. theoretical capacity)
It is being determined by displacing all exchangeable hydrogen (H+) from the colloidal particles, and measuring its amount.
This quantity then represents the potential capacity of the substrate to accept various basic cations into it (like Na+, K+, Ca2+, Mg2+, Al3+).

How to convert mg/kg → mM/kg:

1) determine the content of the substance in the substrate (mg/kg)
2) determine the molar mass of the substance (g/mol)
3) devide the content of the substance in the substrate (mg/kg) by the molar mass of the substance (MH)

ADA Aqua Soil Amazonia

Formula for calculating the saturation: Saturation = T(CEC) - H+
However, in acidic soils the saturation can't be calculated so easily, because in these soils there is usually higher amount of exchangeable hydrogen (H+) in the substrate. In this case, you can calculate the approximate saturation of the substrate as the difference between total sorption capacity (CEC) and the sum of the contents of the main base cations present in the substrate (K+, Ca2+, Mg2+).

CEC (total sorption capacity)   = 269 mM/kg (26.9 mM/100g)

In CEC only the cations are included (K+, Ca2+, Mg2+, Fe2+/Fe3+, NH4+), but not anions (NO3-, PO43-, SO42-).

Potassium (K+)     =    66 mg/kg =   2 mM/kg (   66 g ÷ 39 g/mol)
Calcium   (Ca+)    =   348 mg/kg =  17 mM/kg (  348 g ÷ 20 g/mol)
Magnesium (Mg+)    =    36 mg/kg =   3 mM/kg (   36 g ÷ 12 g/mol)
                                    22 mM/kg (K+, Ca2+, Mg2+)

Molar mass of Ca2+ = 40 g/mol (divalent calcium)
Molar mass of Ca+   = 20 g/mol (monovalent calcium)
In the results of laboratory analysis the values for monovalent calcium (Ca+) are used !
That's why the calcium content in the substrate (or solution) is not being divided by 40 g/mol, but only by halft the value (i.e. 20 g/mol) !
The same applies for magnesium.

Iron  (Fe2+/3+)    = 34100 mg/kg = 610 mM/kg (34100 g ÷ 56 g/mol)
Nitrogen (total)  =  3850 mg/kg = 275 mM/kg ( 3850 g ÷ 14 g/mol)

Iron and nitrogen (nor the ammonia nitrogen) are usually not counted into CEC.

Result:

Potencially free sorption capacity = Total sorption capacity (CEC) – Saturated sorption capacity (sum of K, Ca, Mg)
Potencially free sorption capacity = 247 mM/kg (269 - 22)

Based on all the above data and calculations, we can deduce that it is an acidic, unsaturated ("hungry") substrate, as confirmed by numerous practical experiences with its use in planted tanks, where it rapidly reduces the water hardness for several weeks or even months, and acidifies it, thereby also decreasing its alkalinity. This is due to the fact that it contains a relatively large amount of humic substances (with a higher proportion of fulvic acids) from which a large amount of hydrogen ions (H+) is released into the water, and large quantities of base cations are bound to their place from the water (K+, Ca2+, Mg2+). A large amount of hydrogen ions in water leads logically to the decrease of pH as well as total alkalinity (part of the hydrogen ions is neutralized by bicarbonates whose concentration in the water decreases).

  ADA Aqua Soil Amazonia Powder

Producer: ADA Aqua Design Amano

Marketing description of the substrate: see the previous product

Recommended usage: see the previous product

Characteristics of the analyzed substrate:
Trade nameAqua Soil Amazonia [Powder]
Package3ℓ, 9ℓ
Graininess2-3 mm
Weight0,7? kg/ℓ
Country of purchase Czech Republic
Statenew, in original packaging
Results of the laboratory analysis:
ParameterValueUnitNote
pH4.66strongly acidic reaction
carbonates [CO3]0.2 %low content
N-total3,170   mg/kgsum of all forms of inorganically and organically bound nitrogen (ammonia, nitrite, nitrate and organic nitrogen)
98-99% of the nitrogen in the soil is in the organic form, and only a small part is in the mineral form.
Nitrogen bound in the organic form presents a stock form of N that plants can use only after mineralization.
N-NH4+ mineral148.18mg/kghigh
N-NO3- mineral58.24mg/kg
P-available24.3 mg/kglow content
K-available250   mg/kgsatisfactory content
Ca-available1,371   mg/kglow content
Mg-available178   mg/kgsatisfactory content
Fe-total41,000   mg/kg(average content)
Mn-total1,043   mg/kg
CEC25.71mM/100ghigh cation exchange capacity
Exchangeable H+34.5 mM/100ghydrogen that is in the sorption complex
Cox4.54%very high content (total oxidizable organic carbon)
humus7.8 %very high content (stable organic component of substrate)
Clay [Graininess I]53.5 %→ heavy, clay loam soil
Silt [Graininess II]26.6 %
Sand [Graininess III]19.9 %

  ADA Aqua Soil Amazonia (old)

Producer: ADA Aqua Design Amano

Marketing description of the substrate: see the description for ADA Aqua Soil Amazonia

Recommended usage: see the description for ADA Aqua Soil Amazonia

Characteristics of the analyzed substrate:
Trade nameAqua Soil Amazonia
Aqua Soil Amazonia [Powder]
Package3ℓ, 9ℓ
Graininess2-5 mm
Weight0.7? kg/ℓ
Country of purchase Czech Republic
State1-3 years old
Results of the laboratory analysis:
ParameterValueUnitNote
pH5.83slightly acidic reaction
carbonates [CO3]0.1 %low content
N-total4,770   mg/kgsum of all forms of inorganically and organically bound nitrogen (ammonia, nitrite, nitrate and organic nitrogen)
98-99% of the nitrogen in the soil is in the organic form, and only a small part is in the mineral form.
Nitrogen bound in the organic form presents a stock form of N that plants can use only after mineralization.
N-NH4+ mineral7.14mg/kglow
N-NO3- mineral5.97mg/kg
P-available26.6 mg/kglow content
K-available151   mg/kgsatisfactory content
Ca-available2,503   mg/kggood content
Mg-available680   mg/kgvery high content
Fe-total62,300   mg/kg(average content)
Mn-total1,207   mg/kg
CECmM/100ghigh cation exchange capacity
Exchangeable H+ mM/100ghydrogen that is in the sorption complex
Cox5.61%very high content (total oxidizable organic carbon)
humus9.7 %very high content (stable organic component of substrate)
Clay [Graininess I]33.8 %→ medium, loam soil
Silt [Graininess II]27.8 %
Sand [Graininess III]38.4 %

  Substrate for aquatic plants

Producer: Rašelina a.s.

Marketing description of the substrate:

The substrate for aquatic plants is prepared for growing aquatic plants. It is made of graded river sand, graded transitional, boggy and "white" peat, with the addition of mineral compounds and calcium fertilizers. Contains all major as well as trace nutrients. Prevents the formation of algae. Supports the growth of new plant shoots.

Recommended usage:

We use the substrate for the cultivation of aquatic and coastal plants (e.g.: marsh marigold, Calla palustris, water lily, Sagittaria, Great Manna Grass, etc.) in pond baskets, buckets and gutters.

Characteristics of the analyzed substrate:
Trade nameSubstr. for aquatic plants
Package5ℓ
Graininessdiverse (soil substrate)
Weight0.6? kg/ℓ
Country of purchase Czech Republic
Statenew, in original packaging
Results of the laboratory analysis:
ParameterValueUnitNote
pH5.45acidic reaction
carbonates [CO3]<0.1 %low content
N-total3,920   mg/kgsum of all forms of inorganically and organically bound nitrogen (ammonia, nitrite, nitrate and organic nitrogen)
98-99% of the nitrogen in the soil is in the organic form, and only a small part is in the mineral form.
Nitrogen bound in the organic form presents a stock form of N that plants can use only after mineralization.
N-NH4+ mineral6.87mg/kg(velmi) vysoký
N-NO3- mineral444.05mg/kg
P-available56.0 mg/kgsatisfactory content
K-available109   mg/kgsatisfactory content
Ca-available3,671   mg/kghigh content
Mg-available523   mg/kgvery high content
Fe-total5,100   mg/kg(relatively low content)
Mn-total125   mg/kg
CECmM/100gvery high cation exchange capacity
Exchangeable H+ mM/100ghydrogen that is in the sorption complex
Saturation level   %
Cox6.97%very high content (total oxidizable organic carbon)
humus12.0 %very high content (stable organic component of substrate)
Clay [Graininess I]11.7 %→ light, loamy sand soil
Silt [Graininess II]13.4 %
Sand [Graininess III]74.9 %

  Agro AQUAplants (substrate for aquatic plants)

Producer: Agro CS a.s.

Marketing description of the substrate:

Substrate specially developed for the cultivation of aquatic and marsh plants that is able to provide them an ideal conditions for their growth. It contains a quality compost, sand, clay, and has a modified reaction (pH). A higher content of clay particles contributes to better supplying the plants with nutrients.

Recommended usage: unspecified

Characteristics of the analyzed substrate:
Trade nameAQUAplants
Package20ℓ
Graininessdiverse (soil substrate)
Weight0,6 kg/ℓ
Country of purchase Czech Republic
Statenew, in original packaging
Results of the laboratory analysis:
ParameterValueUnitNote
pH5.55acidic reaction
carbonates [CO3]<0.1 %low content
N-total2,860   mg/kgsum of all forms of inorganically and organically bound nitrogen (ammonia, nitrite, nitrate and organic nitrogen)
98-99% of the nitrogen in the soil is in the organic form, and only a small part is in the mineral form.
Nitrogen bound in the organic form presents a stock form of N that plants can use only after mineralization.
N-NH4+ mineral6.89mg/kglow
N-NO3- mineral2.72mg/kg
P-available69.9 mg/kgsatisfactory content
K-available362   mg/kghigh content
Ca-available3,012   mg/kghigh content
Mg-available1,028   mg/kgvery high content
Fe-total5,200   mg/kg(relatively low content)
Mn-total218   mg/kg
CEC45.54mM/100gvery high cation exchange capacity
Exchangeable H+19.1 mM/100ghydrogen that is in the sorption complex
Saturation level58   %
Cox10.19%very high content (total oxidizable organic carbon)
humus17.5 %very high content (stable organic component of substrate)
Clay [Graininess I]12.1 %→ light, loamy sand soil
Silt [Graininess II]8.9 %
Sand [Graininess III]79.0 %

  Tropica Aquarium Soil

Producer: Tropica.com

Marketing description of the substrate:

Aquarium Soil is a complete bottom layer, which can be used without any additional layer (whether be it a bottom/reserve layer, or top/cover layer). It ensures a proper growth and stimulates red coloration of plants. It lowers the pH value and slightly affects the water chemistry. Thanks to its fine graininess (fraction) plants are easily planted into it.

Recommended usage:

Place the substrate on the bottom of an aquarium in a 4-5 cm thick layer, and change 25-50% of the water min. twice a week during the first 4 weeks after establishing the aquarium.

Characteristics of the analyzed substrate:
Trade nameTropica Aquarium Soil
Package3ℓ, 9ℓ
Graininess2-3 mm
Weight1.0 kg/ℓ
Country of purchase Czech Republic
Statenew, in original packaging
Results of the laboratory analysis:
ParameterValueUnitNote
pH5.11acidic reaction
carbonates [CO3]0.2 %low content
N-total2,530   mg/kgsum of all forms of inorganically and organically bound nitrogen (ammonia, nitrite, nitrate and organic nitrogen)
98-99% of the nitrogen in the soil is in the organic form, and only a small part is in the mineral form.
Nitrogen bound in the organic form presents a stock form of N that plants can use only after mineralization.
N-NH4+ mineral4.61mg/kgmedium
N-NO3- mineral25.12mg/kg
P-available21.8 mg/kglow content
K-available360   mg/kghigh content
Ca-available1,459   mg/kgsatisfactory content
Mg-available247   mg/kghigh content
Fe-total47,200   mg/kg(average content)
Mn-total971   mg/kg
CEC28.08mM/100ghigh cation exchange capacity
Exchangeable H+33.5 mM/100ghydrogen that is in the sorption complex
Cox4.55%very high content (total oxidizable organic carbon)
humus7.8 %very high content (stable organic component of substrate)
Clay [Graininess I]13.8 %→ light, loamy sand soil
Silt [Graininess II]34.4 %
Sand [Graininess III]51.7 %

  Tropica Plant Growth Substrate

Producer: Tropica.com

Marketing description of the substrate:

A concentrate, used under gravel when planning the aquarium. Ensures healthy and long-term growth of aquatic plants. Is neutral and does not affect the KH of pH value of the water. The substrate absorbs nutrients and makes them available to plant roots.

Recommended usage:

Plant Growth Substrate is laid in a 1 cm thick layer on the bottom of the aquarium, that is then capped with at least 3 to 4 cm thick layer of gravel (this upper layer servers as a barrier between the concentrated substrate and the water).

Characteristics of the analyzed substrate:
Trade nameTropica Plant Growth Substrate
Package1ℓ, 2.5ℓ
Graininessdiverse (soil substrate)
Weight1.25 kg/ℓ
Country of purchase Czech Republic
Statenew, in original packaging
Results of the laboratory analysis:
ParameterValueUnitNote
pH7.21neutral reaction
carbonates [CO3]1.5 %medium content
N-total2,310   mg/kgsum of all forms of inorganically and organically bound nitrogen (ammonia, nitrite, nitrate and organic nitrogen)
98-99% of the nitrogen in the soil is in the organic form, and only a small part is in the mineral form.
Nitrogen bound in the organic form presents a stock form of N that plants can use only after mineralization.
N-NH4+ mineral171.17mg/kghigh
N-NO3- mineral1.01mg/kg
P-available67.7 mg/kgsatisfactory content
K-available407   mg/kghigh content
Ca-available4,890   mg/kghigh content
Mg-available234   mg/kggood content
Fe-total75,500   mg/kg(high content)
Mn-total494   mg/kg
CEC19.37mM/100gupper middle cation exchange capacity
Exchangeable H+3.2 mM/100ghydrogen that is in the sorption complex
Saturation level83   %
Cox2.62%high content (total oxidizable organic carbon)
humus4.5 %high content (stable organic component of substrate)
Clay [Graininess I]32.3 %→ medium, loam soil
Silt [Graininess II]16.8 %
Sand [Graininess III]50.9 %

  Shirakura Red Bee Sand

Producer: Hirose s.r.o.

Marketing description of the substrate:

This substrate (soil) was developed specially for breeding shrimps by Takayuki Shirakura. This substrate was created in a special (proprietary) way from various kinds of baked (burnt) soil, and is able to continuously reduce the hardness, alkalinity, and pH of aquarium water for about one year given you change 20% of water every 2 weeks. It contains no added fertilizer. Its highly porous structure provides a large surface area for the settlement of important microorganisms. Other benefits include limiting the growth of algae, greener color of mosses, clearer water, natural color (black and brown). According to the manufacturer, the largest population of bacteria will form in the substrate when using an undergravel filter (UDF) which filters out the entire volume of the tank every 5 minutes.

Recommended usage:

The recommended height of the substrate is at least 4 cm. You should not wash (rinse) the substrate before first use. The substrate ensures ideal conditions for biological filtration and perfect water purification when in combination with an undergravel filter. The important thing is that the substrate should be put evenly on the undergravel filter, so that water can flow through it equally in all places (hills, slopes or other terrain irregularities are not good for proper function of the UDF because the water then flows through only those places where it face the least resistance).

Characteristics of the analyzed substrate:
Trade nameShirakura Red Bee Sand
Package4 kg, 8 kg
Graininess2-4 mm
Weight1 kg/ℓ
Country of purchase Germany
Statenew
Results of the laboratory analysis:
ParameterValueUnitNote
pH5.4 
carbonates [CO3]n/a%
N-totaln/amg/kgsum of all forms of inorganically and organically bound nitrogen (ammonia, nitrite, nitrate and organic nitrogen)
98-99% of the nitrogen in the soil is in the organic form, and only a small part is in the mineral form.
Nitrogen bound in the organic form presents a stock form of N that plants can use only after mineralization.
N-NH4+ mineral2.8 mg/kg
N-NO3- mineral7.4 mg/kg
P-available<1   mg/kg
K-available8   mg/kg
Ca-availablen/amg/kg
Mg-available16   mg/kg
Fe-EDTA120   mg/kg
Mn-total7.1 mg/kg
CECn/amM/100g
Exchangeable H+n/amM/100ghydrogen that is in the sorption complex
Coxn/a%(total oxidizable organic carbon)
humus7.1 %very high content (stable organic component of substrate)
Clay [Graininess I]n/a%
Silt [Graininess II]n/a%
Sand [Graininess III]n/a%
Analyzed: Institut für Boden und Umwelt, 8/2009 (borrowed from the website shirakura-shop.de)

Comparison

Here you can see what is the normal composition of aquatic substrates (bottom sediments) in rivers, reservoirs and lakes:

Example of the chemical composition of bottom sediments from three water reservoirs in Slovakia:
Indicator (unit)Min.Max.Average
organic fraction (%)2.4613.075.26
carbonates (%)11.2534.620.3
Ntotal (g/kg)2.546.864.54
Ptotal (g/kg)0.331.51.03
pH value6.657.57.15
ORP (mV)-188-246-210
Except for pH and ORP all data refer to the dry matter.
Composition of the bottom sediments of four Sumava lakes (upper 5 cm layer analyzed):
Indicator (unit)Min.Max.Average
pH value6.16.26.15
loss on ignition of dry matter (%)55.365.764.0
Ptotal (g/kg)1.84.02.6
iron (g/kg)10.033.423.1
aluminium (g/kg)39.847.643.0
calcium (g/kg)1.52.72.2
Except for pH and ORP all data refer to the dry matter.
Example of the upper layer of sediments (0-1 cm) in 37 Tatra lakes [Slovakia] (all values are in g/kg):
ElementMin.Max.Average
C18.02408.34124.90
N1.4040.8811.06
P0.563.901.89
Ca0.526.412.85
Mg0.905.013.06
K0.592.191.45
Al6.2150.1831.30
Fe3.3587.1322.34
Mn0.0534.281.76
Concentrations of selected metals and total phosphorus in the dry matter of sediments in 12 profiles of Labe river in 2001 (all values in g/kg):
IndicatorMin.Max.Average
Cu0.060.310.14
Fe18.9045.7030.97
Mn0.156.211.30
Ni0.030.100.05
Zn0.252.280.78
Ptotal1.205.002.88

  • The content of N-total is about 4.5 g/kg on average (while in the uppermost layer it can be even higher).
    In the topsoil there is 1-3 g/kg N in average (of which only 1-2% is in available, mineral form).
  • The content of P-total is about 1-3 g/kg on average, but the amount of available P will of course be much lower.
  • The content of Fe-total is 20-30 g/kg on average.
  • Ca content is around 2-3 g/kg on average.
  • pH value is typically slightly acidic or neutral.

Now compare the above values with the nutrient content in selected aquarium substrates:

On aquaristic Internet forums you can quite often come across the argument that if you are serious with the cultivation of aquatic plants, you should forget about other substrates, and get ADA Aqua Soil that is literally packed with nutrients.

If you compare the results of laboratory analyses with the nutrient content in river sediments or common agricultural topsoil, you will find that most of the aquarium substrates lag behind in nutrients. I hope these data will help destroy another myth (about the supposed superiority of some aquarium substrates), and establish a dominance of common sense again.

Most of the tested aquarium substrates has a relatively acidic pH with a high content of acidic H+ ions, and with high cation sorption capacity. Humus content is around 7-12% (exceptionally even higher). What was similar in most of the tested substrates is the pH value (~5), humus content (7-12%), total nitrogen content (2-4%), and total iron (4-7%). What was in fact significantly different is the content of most available minerals (NH4+, NO3-, P, K, Ca, Mg, Fe, Mn).

While the substrates ADA Aqua Soil Amazonia and Tropica Plant Growth Substrate have a relatively high content of ammonia nitrogen, Substrate for aquatic plants from Raselina.cz company has a relatively high content of nitrate nitrogen. This may be beneficial for more substantial initial plant nutrition, but risky for animals, because it can be assumed that these nutrients will have a tendency to get into the soil solution once the substrate is flooded, and then from there into the water column. Higher content of mineral nitrogen in the substrate therefore lasts usually only for a relatively short period of time (estimated to several weeks to months). It should be said that even the total nitrogen content is still below average when compared with aquatic sediments.

Czech substrates for aquatic plants (Agro CS as well as Raselina.cz) have substantially lower content of total iron (Fe) and manganese (Mn) compared with other tested substrates, but this is not necessarily an evidence of low content of available iron and manganese.

While the pH is acidic with the substrates of Tropica (Aquarium Soil), Agro (AQUA plants), and Shirakura, with the substrates of ADA (Amazonia) it is highly acidic. These substrates are probably made of acid soils characterized by unsaturated form of humus with a predominance of fulvic acids. Neutral reaction (pH of 5.7 to 8.3) is usually common in chernozem (black earth) characterized by saturated form of humus. In comparison with the water sediments the tested aquarium substrates (with one exception) have much lower pH.

Cation exchange capacity (CEC) is high in practically all substrates tested, except for the Tropica Plant Growth Substrate (with 'upper middle' CEC) and Agro AQUAplants (with 'very high' CEC). Substrates ADA Aqua Soil Amazonia and Tropica Aquarium Soil also have a very high content of exchangeable hydrogen (H+) – higher than the cation exchange capacity (CEC) – which means that they are very acidic and "hungry". Their use in the aquarium will lead to a rapid drop in pH (acidification of water), till most of the hydrogen will be displaced from the substrate and replaced by potassium, calcium and/or magnesium, whereby the substrate is largely saturated. This process will be speeded up when using a harder water with a higher content of K+, Ca2+ or Mg2+ ions. The most saturated substrate (by more than 80%) is Tropica Plant Growth Substrate, which also has (as the only one) a slightly alkaline pH.

When you compare the new ADA substrates (columns #1 and #2) with a several years old and used ADA substrate (column #3), which is a mix of both previous substrates, you will find that in this substrate pH and total humus content increases over time (probably due to an accumulation of detritus). In this substrate the concentration of most available nutrients (mainly calcium and magnesium) also increases over time. Moreover, this substrate seems to be literally a "trap" for iron (the total Fe content rose by about 65% after 1-3 years).

Commentary

Tank cycling using the soil substrates with low content of mineral (ammonia or nitrate) nitrogen will be probably less problematic, because only a small amount of this nutrient will be leaching into the water column from them. On the other hand, the substrates with higher content of these nutrients may be more suitable for the initial "boost" of plants in the planted tanks, since they will supply them with sufficient amount of mineral nitrogen during the first few weeks.

As far as commercial substartes are concerned, it is important to note how easily a proper marketing strategy can change an ordinary (below-average) soil substrate into something extra. When you read the promotional description of ADA or Tropica substrates, you'll easily get the impression that this substrate is such an extraordinary product that it is worth the exorbitant money. To the contrary, after your read the description of an "ordinary" Substrate for aquatic plants or Agro AQUAplants, you'll get the impression that it is probably not a good idea to use such a substrate in your tank. However, in fact these "ordinary" soil substrates knock both of the commercial products into a cocked hat in most parameters.

If I were to recommend something to hobbyists, I would encourage them to use a common sense, and don't get screwed by catchy advertisment. This does not apply with substrates only, but with decorations, equipment, fertilizer as well as with all possible miraculous snake oils and gadgets.

Marcel Goliaš © 2019