How to Create an Underwater Cave for a Fish Aquarium

Written by gayle baillargeon
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How to Create an Underwater Cave for a Fish Aquarium
A cave provides a safe hiding place for fish. (Jupiterimages/ Images)

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.

Skill level:

Things you need

  • Flat stones
  • Scrub brush
  • Aquarium silicone

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  1. 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. 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. 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 centre 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. 4

    Let the silicone set overnight before moving the cave.

  5. 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.

Tips and warnings

  • Create a cave quickly with a new terracotta flower pot. Enlarge the drainage hole and bury one side of the pot in the gravel.
  • It is safer for fish if the cave is open at the back to allow an alternate escape route.
  • Contaminated rocks can slowly leach poison into the water and kill the fish. Stay away from rocks that may have come in contact with pesticides or fertilisers, show traces of rust, contain water-soluble minerals such as salt or have sharp edges.
  • Do not use detergent or bleach or a brush that has been in contact with any cleaners.

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