Decorative fish gravel is used in
aquariums for a number of purposes. It is, of course
decorative in its own right. It can be natural in appearance or it can come in bright, even neon colors. It can
compliment the color of the fish or the decor of the room the aquarium is in. Tastes vary.
In addition to direct decorative effects there are indirect effects that enhance the appearance of the aquarium by hiding
waste products and excess food.
Gravel can also be used to anchor underwater
plants to the bottom of the aquarium. This allows roots to grow in the
substrate for rooted plants and it allows the fishkeeper to cover the uglier aspects of bunched (non rooted) aquarium plants which are often held together with rubber bands or soft lead bands.
Decorative fish gravel can also serve functional purposes. Part of an aquarium’s upkeep is the
nitrogen conversion cycle by which
bacteria break harmful waste products down into less harmful ones. One type of
filter called an
under gravel filter makes use of the flow of water through a
substrate of small grade (1 - 2 mm) gravel. Since the gravel is small there is a lot of
surface area for bacteria to live on. As the water flows through the gravel the bacteria which are living on the gravel break down harmful waste products to less harmful waste products. Another practical use of decorative gravel is to raise the
pH of the water. Some species of
fish require a pH higher than the normal 7 of most
tap water. Certain types of rocks and/or gravel
leach chemicals that raise the pH.
Driftwood or boiled
sphagnum moss is used to lower pH for fish who prefer that environment.
The breakdown of the waste products hidden by the gravel is not enough to maintain the aquarium, the waste products must also be removed using a
gravel vacuum and
partial water changes of 10% to 25% must be done periodically. The decorative gravel only hides the waste, it is still there contaminating the water.