How to Test Rocks for Aquarium Use

Rock formations are among the most attractive decorative pieces for the tropical aquarium. The majority of them are "aquarium-safe," which means they are basically inert and will not mess with the water composition of the tank. These include quartz, slate, lava rock, granite, petrified wood and most of the gemstone minerals. The types of rock that are not safe to use in fish tanks are those that leach calcium and magnesium into the water. A few easy tests can be done to check if a particular rock is safe for fish or not.

Things You'll Need

  • Muriatic acid
  • White vinegar
  • PH test kit
  • Nitrate test kit
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Instructions

    • 1

      Start with a clean rock. Wash the rock under clean running water to remove dust and debris that could influence the test results.

    • 2

      Submerge the rock in water. Put the rock in a container with enough water to immerse it. Test the pH level of the water, then test again after two weeks. If the pH reading remains the same, it means the rock does not leach calcium and is safe for the fish tank.

    • 3

      Pour concentrated white vinegar on various areas of the rock. If the vinegar bubbles, the rock has carbonate that will alter the water conditions of the aquarium and therefore is not safe for the average tropical fish.

    • 4

      Place a few drops of 20 percent muriatic acid on various areas of the rock. If the surface sizzles or bubbles, the rock contains calcium that will affect the water conditions of the fish tank.

    • 5

      Place a few drops of the nitrate testing solution that typically contains hydrochloric acid. If the surface of the rock bubbles, it is not aquarium-safe.