What Are Base Rocks?

The term "base rocks," also known as foundation rocks, refers to rocks free from living organisms and algae, minus the possible presence of some bacteria. Fish tank owners use natural and artificial base rocks to create aquarium environments that mimic natural seascapes.

  1. The Facts

    • Base rocks, scientifically known as aragonite rocks, are composed of calcium carbonate. This type of rock typically forms in hot spring deposits and gypsum beds, occurring as an evaporate deposit much like a pearl. Aragocrete rocks -- made from gravel, low-alkaline cement and plastic sawdust -- serve as man-made alternatives to base rocks. When base rocks collect organisms such as coralline or other algae, they become live rocks.

    Identification

    • Base rocks come in all sorts of sizes, but are usually porous and have an irregular, bumpy shape. Base rocks come in light earth-toned hues, including beige, white, off-white and gray. Some aragonite rocks have very subtle green or blue shades. The hardness of base rocks varies from very soft to medium hard. Over time, these lightweight rocks collect coralline and other types of algae, which give foundation rocks a reddish blue or violet hue.

    Uses

    • Base rocks lend themselves to saltwater aquarium rocking, or populating the aquarium with various types of rock. As its name implies, base rocks serve as the base layer of rock, usually topped by more expensive and colorful decorative live rocks, known as aquacultured rocks. Aquarium owners use aragocrete base rocks, which can be made in custom shapes, as a base layer or as decorative aquarium ornaments such as sculptures and arches.

    Benefits and Considerations

    • When compared to other rocks that aquarium owners use in saltwater fish tanks, base rocks are the most affordable. Aquarium owners can alter the size and shape of base rocks with a hammer and chisel -- without damaging the rock's integrity or any organisms that may have collected on the rock's surface. Aquarium owners may also use light brown tufa, limestone rubble and red lava rocks as base rocks.