How to Create an Underwater Cave for a Fish Aquarium

A well-designed tank provides both an interesting and safe habitat for aquarium fish. Adding a cave will not only give more timid fish a safe haven but will add another dimension to the way the fish interact. A natural arrangement of granite or sandstone rocks creates a focal point. Constructing a series of caves and rock walls helps to camouflage the back wall of the aquarium. Watching the ongoing game of hide and seek as fish swim in and out of caves will provide hours of fascinating viewing.

Things You'll Need

  • Flat stones
  • Scrub brush
  • Aquarium silicone
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Instructions

    • 1

      Wash the flat rocks with a new scrub brush and clean water to remove all dirt and debris from the crevasses of the rocks. Do not use soap or any other cleaning solution.

    • 2

      Position two rocks about three inches apart. Bridge the gap between the two stones by placing a third stone on top of the two base stones. The cave should be at least 2 inches high and 3 inches wide so a fish cannot get stuck inside. Continue arranging the stones until you are pleased with the formation.

    • 3

      Cement the rocks together with aquarium silicone so there is no danger of a rock falling on a fish. Apply a layer of silicone to the center of the area where two rocks touch, using just enough silicone so the rocks are well-anchored. If you apply too much silicone, it will show when you press the rocks together.

    • 4

      Let the silicone set overnight before moving the cave.

    • 5

      Place the cave in the aquarium, leaving enough space on all sides so fish have swimming space and won't get stuck on a rock.