Glossary – Aquarium Substrate
In the context of an aquarium, substrate refers to the material used on the tank bottom. The material you use for your substrate can affect water chemistry, filtration, be the reason your fish are healthy, not to mention contribute to the visual appeal of your aquarium. You should make sure that you use only natural aquarium gravel for the substrate, which is chemically inert.
Aquarium substrate allows the fish to be oriented in the water, knowing top and bottom. Fish tend to become irritated by a clear bottomed aquarium, because of reflections and increased light sources.
The substrate you use can vary depending on the fish that you have the kind of aquarium that you are planning. For instance, fish like the Congo Tetra being a rather shy kind of fish prefer a dark substrate. Some fish, such as bottom feeders require finer gravel, while others are okay with larger gravel. Peat for instance, can mimic the conditions of soft water.
If you are planning a planted aquarium, you would need finer gravel to help provide the roots some anchor. A good choice for a planted tank, is to use finer gravel with fertilizer at the bottom, topped with thicker gravel.
Other useful information sources:
Aquarium Substrate on Algone
Substrate (aquarium) on Wikipedia
