Aquarium Gravel.

Substrate or gravel in your aquarium plays an important role in the natural biological cycle. Beneficial bacteria often grow along the top of the gravel bed and will help to break down wastes produced by the fish in the aquarium . Gravel is also useful in helping to anchor live plants and other aquarium decorations..

Substrates are available in many shapes and sizes. Large grained materials should not be used because debris and food that is uneaten can get trapped between the granules and pollute the water.

Small grained substrates, such as sand, will pack down tightly , clog the water flow and cause a rise in unwanted anaerobic bacteria, a type of bacteria that thrives without oxygen. Sand that is packed tightly on the bottom of the aquarium is also harmful to plants because it doesn't allow enough oxygen and water to circulate around the plant roots. If sand is used, it should be laid down in a very thin layer.

A gravel or substrate that is 3 millimeter in diameter is a good size to use in the aquarium. A 1 inch layer on the bottom filled with gravel this size will be sufficient to decorate the aquarium and serve as anchorage for the plants.