Substrate (aquarium)
Encyclopedia
The substrate of an aquarium
refers to the material used on the tank bottom. It can affect water chemistry, filtration, and the well-being of the aquarium's inhabitants, and is also an important part of the aquarium's aesthetic appeal. The appropriate substrate depends on the type of aquarium; the most important parameter is whether the aquarium contains fresh water
or saltwater.
Some substrates are used to alter water chemistry. Crushed coral and coral sand both contain calcium carbonate
, which will raise the carbonate hardness
and buffer the pH
. Peat
may be used in some aquaria to mimic some soft water habitats.
Substrate may also be used as part of a biological filtration system. Beneficial bacteria colonize all aquarium surfaces that are exposed to aerated water, including the substrate. Because the numerous particles have a high surface area, substrates are often employed in biological filtration. Some common types of filtration involving the substrate include the undergravel filter and the deep sand bed
.
Planted tanks require a substrate that will remain loose enough for plant roots to penetrate it. The substrate should be chemically inert and free of sharp edges. Fine gravel (1–2 mm) is preferred by some aquarists because coarser substrates allow debris to settle within the gaps between grains, which is particularly difficult to clean in a planted aquarium. Sloping the substrate so it is most shallow in front accommodates larger plants with correspondingly larger root systems in the back. The substrate for plants should be at least 5 cm (2 in) deep. Often, a lower layer of richer substrate such as potting soil, peat, vermiculite, or certain types of clay are used as a source of iron and trace elements for plant roots.
In breeding tanks for egg-scattering species, a layer of marbles is sometimes used as a substrate, allowing the eggs to fall into the gaps between the marbles where the parents cannot eat them. Quarantine tanks (sometimes called hospital tanks) often use no substrate at all. This assists in keeping the aquarium as clean as possible as well as monitoring of fish excrements.
Fish of the species Pelvicachromis taeniatus were shown to be able to recognize olfactory traces left behind by substrate, even in clear water; highlighting that the presence of substrate is important for fish kept in tanks. This method is beneficial to increase fish activity drastically in empty tanks.
aquaria, gravel is the most common substrate. To prevent damage to fish, gravel should not be sharp. Aquarium gravel can be as coarse as pea-sized or as fine as 1–2 mm. It is available in a number of colors, and may be naturally colored or dyed, and may have a polymer seal to ensure it does not affect water chemistry. Gravel sold specifically for use in aquaria is chemically inert. It is commonly composed of quartz or other lime
-free minerals. If the gravel is rough or sharp, it is not suitable for bottom-dwelling fish that like to sift the substrate or dig.
When growing aquatic plants, the Cation Exchange Capacity (CEC) is also an important thing to consider when choosing a substrate. CEC is the ability to adsorb positively charged nutrient ions (so high CEC is good). This means the substrate will hold nutrients and make them available for the plant roots. It doesn’t indicate the amount of nutrients the substrate contains.
Shell grit, crushed limestone
, crushed marble
, crushed coral
skeletons, coral sand, and oolitic
aragonite
substrates are possible choices. Because calcium carbonate
, the primary component of these substrates, increases water hardness
and pH
, these are used most often for hard water species, such as those for African rift lake
cichlids or for saltwater fish and invertebrates. Some invertebrates such as mollusks or stony corals also use the calcium
and strontium
released. Calcium carbonate substrates are poorly suited to aquaria housing most other freshwater aquarium fish, particularly river species, which are adapted to soft water.
Peat
, or decomposed plant matter, is used most commonly in soft water or blackwater river
systems, such as those mimicking the Amazon River
basin. In addition to being soft in texture and therefore suitable for demersal (bottom-dwelling) species such as Corydoras
catfish, peat is reported to have a number of other beneficial functions in freshwater aquaria. It softens water by acting as an ion exchange
r, it contains substances good for plants and for the reproductive health of fishes, and can even prevent algae growth and kill microorganisms. Peat often stains the water yellow or brown due to the leaching of tannin
s.
Sand
is often recommended for use with certain species, such as the river stingrays of family Potamotrygonidae
, which bury themselves in the fine substrate. However, these species can be successfully kept with coarser substrates as well.
In some aquaria, different substrates are used in different parts of the tank. For example, peat can be used in one corner, while gravel in another portion allows rooted plants.
Aquarium
An aquarium is a vivarium consisting of at least one transparent side in which water-dwelling plants or animals are kept. Fishkeepers use aquaria to keep fish, invertebrates, amphibians, marine mammals, turtles, and aquatic plants...
refers to the material used on the tank bottom. It can affect water chemistry, filtration, and the well-being of the aquarium's inhabitants, and is also an important part of the aquarium's aesthetic appeal. The appropriate substrate depends on the type of aquarium; the most important parameter is whether the aquarium contains fresh water
Fresh Water
Fresh Water is the debut album by Australian rock and blues singer Alison McCallum, released in 1972. Rare for an Australian artist at the time, it came in a gatefold sleeve...
or saltwater.
Functions and considerations
Substrates are added to most aquaria principally for the increase in beneficial bacteria this provides. However, substrates can also have a variety of direct effects on water quality by releasing substances into the water, absorbing substances from the water, or reacting chemically with substances from other sources. Substrates can also have indirect effects on a system's health; dark-colored substrates, for example, are considered by some to be better for fish, as the fish display more colorfully by comparison, and are less likely to behave timidly. Apart from all other considerations, substrates are frequently chosen for their aesthetic qualities.Some substrates are used to alter water chemistry. Crushed coral and coral sand both contain calcium carbonate
Calcium carbonate
Calcium carbonate is a chemical compound with the formula CaCO3. It is a common substance found in rocks in all parts of the world, and is the main component of shells of marine organisms, snails, coal balls, pearls, and eggshells. Calcium carbonate is the active ingredient in agricultural lime,...
, which will raise the carbonate hardness
Carbonate hardness
Carbonate hardness, or carbonate alkalinity is a measure of the alkalinity of water caused by the presence of carbonate and bicarbonate anions. It is usually expressed either as parts per million , or in degrees KH...
and buffer the pH
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...
. Peat
Peat
Peat is an accumulation of partially decayed vegetation matter or histosol. Peat forms in wetland bogs, moors, muskegs, pocosins, mires, and peat swamp forests. Peat is harvested as an important source of fuel in certain parts of the world...
may be used in some aquaria to mimic some soft water habitats.
Substrate may also be used as part of a biological filtration system. Beneficial bacteria colonize all aquarium surfaces that are exposed to aerated water, including the substrate. Because the numerous particles have a high surface area, substrates are often employed in biological filtration. Some common types of filtration involving the substrate include the undergravel filter and the deep sand bed
Deep sand bed
A deep sand bed is, by Ronald L Shimek, PhD, in Reefkeeping online magazine a filtration method used in some saltwater aquariums. A deep sand bed, similar to the Berlin Method, is designed to cultivate anaerobic bacteria in the bottom layers of sand, converting nitrate to nitrogen gas to remove...
.
Planted tanks require a substrate that will remain loose enough for plant roots to penetrate it. The substrate should be chemically inert and free of sharp edges. Fine gravel (1–2 mm) is preferred by some aquarists because coarser substrates allow debris to settle within the gaps between grains, which is particularly difficult to clean in a planted aquarium. Sloping the substrate so it is most shallow in front accommodates larger plants with correspondingly larger root systems in the back. The substrate for plants should be at least 5 cm (2 in) deep. Often, a lower layer of richer substrate such as potting soil, peat, vermiculite, or certain types of clay are used as a source of iron and trace elements for plant roots.
In breeding tanks for egg-scattering species, a layer of marbles is sometimes used as a substrate, allowing the eggs to fall into the gaps between the marbles where the parents cannot eat them. Quarantine tanks (sometimes called hospital tanks) often use no substrate at all. This assists in keeping the aquarium as clean as possible as well as monitoring of fish excrements.
Fish of the species Pelvicachromis taeniatus were shown to be able to recognize olfactory traces left behind by substrate, even in clear water; highlighting that the presence of substrate is important for fish kept in tanks. This method is beneficial to increase fish activity drastically in empty tanks.
Types of substrate
For freshwaterFresh Water
Fresh Water is the debut album by Australian rock and blues singer Alison McCallum, released in 1972. Rare for an Australian artist at the time, it came in a gatefold sleeve...
aquaria, gravel is the most common substrate. To prevent damage to fish, gravel should not be sharp. Aquarium gravel can be as coarse as pea-sized or as fine as 1–2 mm. It is available in a number of colors, and may be naturally colored or dyed, and may have a polymer seal to ensure it does not affect water chemistry. Gravel sold specifically for use in aquaria is chemically inert. It is commonly composed of quartz or other lime
Lime (mineral)
Lime is a general term for calcium-containing inorganic materials, in which carbonates, oxides and hydroxides predominate. Strictly speaking, lime is calcium oxide or calcium hydroxide. It is also the name for a single mineral of the CaO composition, occurring very rarely...
-free minerals. If the gravel is rough or sharp, it is not suitable for bottom-dwelling fish that like to sift the substrate or dig.
When growing aquatic plants, the Cation Exchange Capacity (CEC) is also an important thing to consider when choosing a substrate. CEC is the ability to adsorb positively charged nutrient ions (so high CEC is good). This means the substrate will hold nutrients and make them available for the plant roots. It doesn’t indicate the amount of nutrients the substrate contains.
Shell grit, crushed limestone
Limestone
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....
, crushed marble
Marble
Marble is a metamorphic rock composed of recrystallized carbonate minerals, most commonly calcite or dolomite.Geologists use the term "marble" to refer to metamorphosed limestone; however stonemasons use the term more broadly to encompass unmetamorphosed limestone.Marble is commonly used for...
, crushed coral
Coral
Corals are marine animals in class Anthozoa of phylum Cnidaria typically living in compact colonies of many identical individual "polyps". The group includes the important reef builders that inhabit tropical oceans and secrete calcium carbonate to form a hard skeleton.A coral "head" is a colony of...
skeletons, coral sand, and oolitic
Oolite
Oolite is a sedimentary rock formed from ooids, spherical grains composed of concentric layers. The name derives from the Hellenic word òoion for egg. Strictly, oolites consist of ooids of diameter 0.25–2 mm; rocks composed of ooids larger than 2 mm are called pisolites...
aragonite
Aragonite
Aragonite is a carbonate mineral, one of the two common, naturally occurring, crystal forms of calcium carbonate, CaCO3...
substrates are possible choices. Because calcium carbonate
Calcium carbonate
Calcium carbonate is a chemical compound with the formula CaCO3. It is a common substance found in rocks in all parts of the world, and is the main component of shells of marine organisms, snails, coal balls, pearls, and eggshells. Calcium carbonate is the active ingredient in agricultural lime,...
, the primary component of these substrates, increases water hardness
Hard water
Hard water is water that has high mineral content . Hard water has high concentrations of Ca2+ and Mg2+ ions. Hard water is generally not harmful to one's health but can pose serious problems in industrial settings, where water hardness is monitored to avoid costly breakdowns in boilers, cooling...
and pH
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...
, these are used most often for hard water species, such as those for African rift lake
Rift lake
A rift lake is a lake formed as a result of subsidence related to movement on faults within a rift zone, an area of extensional tectonics in the continental crust. They are often found within rift valleys and may be very deep...
cichlids or for saltwater fish and invertebrates. Some invertebrates such as mollusks or stony corals also use the calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
and strontium
Strontium
Strontium is a chemical element with the symbol Sr and the atomic number 38. An alkaline earth metal, strontium is a soft silver-white or yellowish metallic element that is highly reactive chemically. The metal turns yellow when exposed to air. It occurs naturally in the minerals celestine and...
released. Calcium carbonate substrates are poorly suited to aquaria housing most other freshwater aquarium fish, particularly river species, which are adapted to soft water.
Peat
Peat
Peat is an accumulation of partially decayed vegetation matter or histosol. Peat forms in wetland bogs, moors, muskegs, pocosins, mires, and peat swamp forests. Peat is harvested as an important source of fuel in certain parts of the world...
, or decomposed plant matter, is used most commonly in soft water or blackwater river
Blackwater river
A blackwater river is a river with a deep, slow-moving channel that flows through forested swamps and wetlands. As vegetation decays in the water, tannins are leached out, resulting in transparent, acidic water that is darkly stained, resembling tea or coffee. Most major blackwater rivers are in...
systems, such as those mimicking the Amazon River
Amazon River
The Amazon of South America is the second longest river in the world and by far the largest by waterflow with an average discharge greater than the next seven largest rivers combined...
basin. In addition to being soft in texture and therefore suitable for demersal (bottom-dwelling) species such as Corydoras
Corydoras
Members of the South American Corydoras genus are freshwater temperate and tropical catfish in the armored catfish family , and are commonly referred to as corydorases, cories, or cory catfish.-Taxonomy:...
catfish, peat is reported to have a number of other beneficial functions in freshwater aquaria. It softens water by acting as an ion exchange
Ion exchange
Ion exchange is an exchange of ions between two electrolytes or between an electrolyte solution and a complex. In most cases the term is used to denote the processes of purification, separation, and decontamination of aqueous and other ion-containing solutions with solid polymeric or mineralic 'ion...
r, it contains substances good for plants and for the reproductive health of fishes, and can even prevent algae growth and kill microorganisms. Peat often stains the water yellow or brown due to the leaching of tannin
Tannin
A tannin is an astringent, bitter plant polyphenolic compound that binds to and precipitates proteins and various other organic compounds including amino acids and alkaloids.The term tannin refers to the use of...
s.
Sand
Sand
Sand is a naturally occurring granular material composed of finely divided rock and mineral particles.The composition of sand is highly variable, depending on the local rock sources and conditions, but the most common constituent of sand in inland continental settings and non-tropical coastal...
is often recommended for use with certain species, such as the river stingrays of family Potamotrygonidae
Potamotrygonidae
River stingrays are Neotropical freshwater fishes of the Potamotrygonidae family .They are native to northern, central and eastern South America, living in rivers that drain into the Caribbean, and into the Atlantic as far south as the Río de la Plata in Argentina...
, which bury themselves in the fine substrate. However, these species can be successfully kept with coarser substrates as well.
In some aquaria, different substrates are used in different parts of the tank. For example, peat can be used in one corner, while gravel in another portion allows rooted plants.