Substrate (aquarium)

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.

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.

Often, a lower layer of richer substrate such as potting soil, peat, vermiculite, or certain types of clay is used as a source of iron and trace elements for plant roots.

[1] When growing aquatic plants, the Cation Exchange Capacity[8] (CEC) is also an important thing to consider when choosing a substrate.

Calcium carbonate substrates are poorly suited to aquaria housing most other freshwater aquarium fish, particularly river species, which are adapted to soft water.

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 exchanger, it contains substances good for plants and for the reproductive health of fishes, and can even prevent algae growth and kill microorganisms.

[4] Sand is often recommended for use with certain species, such as the river stingrays of family Potamotrygonidae, which bury themselves in the fine substrate.

They mimic the natural environments of aquatic creatures and create a stress free and pH balancing environment for flora and fauna by tinting the water column colour to a reddish hue with the release of beneficial tannin that certain aquatic life prefer.