Substrate (aquarium bed)
The material that covers the bottom of the aquarium. It influences aesthetics, water chemistry, plant growth and fish well-being.
Detailed explanation
The choice of substrate is not just aesthetic. The type of bottom influences pH, KH, plant growth and fish behaviour.
In marine aquariums the main options are coral sand (aragonite) and live sand. Aragonite releases calcium carbonate keeping the pH stable. The ideal grain size is 1-2mm: fine enough for aesthetics but not so fine as to compact and create anoxic areas. The layer should not exceed 3-4 cm unless a DSB (Deep Sand Bed) for denitrification is desired.
Bare bottom is a popular choice on the reef. Eliminates the risk of debris accumulation in the substrate and facilitates cleaning. The disadvantage is that a substrate for the bacteria is lost and the aesthetics is affected.
In tropical freshwater aquariums with plants, the nutrient substrate is essential. Products such as ADA Amazonia, Tropica Aquarium Soil or JBL Manado provide nutrients to the roots. These allophane substrates slightly lower pH and KH, perfect for Amazonian plants and fish.
Classic gravel (2-5mm) works well for aquariums without fussy plants. It should be rinsed well before use to remove dust.
For Corydoras and other bottom fish with delicate barbels, fine, rounded sand is needed. Sharp gravel can injure the barbels causing infections.
In ponds the natural bottom with coarse gravel is the best choice. Avoid garden soil that releases too many nutrients.
Do not mix substrates with very different grain sizes: the finer one will always end up under the larger one due to gravity.