Decorative fish gravel
is used in aquarium
s 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 product
s and excess food. Gravel
can also be used to anchor underwater plant
s 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 chemical
s 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 change
s of 10% to 25% must be done periodically. The decorative gravel only hides the waste, it is still there contaminating the water.