Natural Aquarium Rock

Using rock will reward you with unique natural decorations for use in the aquarium. Commonly acquired stones are generally non-toxic to fish, but can dissolve to increase pH and hardness. This article will help you choose the correct rocks for fish tanks.

If you want to check your ornament for pH reactivity you can perform an easy test. Take some water from the same pH as your aquarium. Soak the stone in a small volume of water and check the pH over a few days. If there are no fluctuations it will indicate it's suitability as an inert aquarium ornament.

Alternatively you can drop a small amount of acid on the rock and see if it bubbles. A dash of hydrochloric acid dabbed on the ornament will be perfect.

Some rocks can be taken advantage of as a method of buffering alkaline aquariums. Rocks which act as a buffer dissolve in the presence of free hydrogen ions. They are generally calcium carbonate sedimentary rocks such as limestone. These rocks are undesirable in aquariums set up to house acid loving aquarium fish.

Calcium carbonate rocks in the aquarium can also increase water hardness. It is best to exclude them from fish tanks housing soft water aquarium fish.

Completely inert rocks are generally produced from volcanic origins. They include granite, quartz, basalt and many semi precious gemstones such as amethyst and citrine. Slate is another inert rock though this is sedimentary in origin. All of these make excellent aquarium ornaments.

Aggregate rocks may or may not be suitable as ornaments. Tightly compacted construction grade sandstone is suitable as an aquarium ornament. Younger crumbly sandstone will soon return to it's sandy beginnings.

Home Made Rock Decoration

You may wish to bond several stones together to create just the right aquarium ornament. Instructions are available for making objects such as the archway in the photograph.

Further information > How to make rock ornaments

If in doubt go for the classic stone decoration theme for fish tanks. Use sheets of slate to form a cave and then add a few large rounded stones to cover the floor. An all rock theme such as this can be recreated in virtually any aquarium.

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