Can You Use Creek Rock in a Freshwater Aquarium?

Rocks consist of a mix of different minerals that combined over time. Creek rocks are typically inert in water and normally have a smooth texture. They do not disintegrate or alter the chemical composition of water. Aquarium enthusiasts can find rocks of varying sizes in an average creek and can combine large and small rocks to create an aesthetically pleasing underwater landscape. Although you can often place creek rocks directly into an aquarium, it is best to test the rocks first.

  1. Water Resistance

    • Creek rocks are normally water-resistant. However, a rock or stone that flakes or crumbles in water is not ideal for aquarium use. You can check to see whether a creek rock is water-resistant by washing it down with a high-pressure water hose. Scrub the rock with a stiff- bristle brush as well and place it in a bucket of water overnight. If it sheds any of its surface when you scrub it again the following day, it is not suitable for use in the aquarium.

    Carbonate Content

    • A rock collected from a creek tends to have no effect on the chemistry of aquarium water. If you want to use a rock in a tank with water at a pH below 6.5, the rock must not cause the pH of the water to rise. Test your creek rock to make sure it does not contain carbonate in any form. To test, drip dilute muriatic acid, which is available in pool-supply and hardware stores, on the rock. A rock that contains carbonate will immediately begin to fizz. Always wear gloves when working with muriatic acid.

    Metal Content

    • Examine any rock that you remove from a creek for signs of metals. Rocks that contain metals have a shiny appearance either in part or as a whole. Copper, lead and other metals in their free ionic forms are toxic to aquarium creatures. Aquarium water with a pH of less than 7.0 activates any metals contained in a rock. The fish̵7;s metabolism will absorb the molecules of these metals. Pyrite, which possesses a brassy yellow metallic luster, occasionally occurs in rocks that are otherwise safe to use in aquariums. Pyrite, which is toxic, will leach metals into aquariums. Do not collect rocks from creeks or watercourses that flow downstream from old mine dumps.

    Advantages and Disadvantages

    • One of the primary advantages to using creek rocks is that they help in building a habitat for fish. Many fish species are territorial and use rocks as a home base. Some fish lay their eggs on or near solid objects such as rocks; others, such as catfish, feed on algae that grow on rocks. Fish that share a community aquarium enjoy hiding or retreating behind rocks occasionally, so that they are not permanently in each other's presence. In addition, attractive creek rocks give an aquarium an aesthetically pleasing look. The major disadvantage to using creek rocks is that some will leach material into the aquarium that alters the pH of the water. Aquarists need to avoid these specimens.