How to DIY an Aquarium Background with Lava Rocks

Written by corinne cooke
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How to DIY an Aquarium Background with Lava Rocks
(Balancing Stones image by kuhar from

Lava rocks are formed from solidified lava. Such rocks are aquarium safe because they are inert, that is they will not affect the pH level of the aquarium. As a result of its aquarium-safe properties, lava rocks are often used in aquariums to create a natural underwater appearance. Additionally, lava rocks have the added benefit of decreasing the built-up nitrates in your aquarium after six months; high nitrate levels are harmful to fish and promote algae growth. You can customise your own aquarium with a lava-rock background and a built-in cave network to add a new dimension to your fish tank and provide interesting areas for your fish to explore.

Skill level:

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Things you need

  • Brown vinyl guttering
  • Aquarium-safe black silicone
  • Caulking gun
  • Jigsaw
  • Drill with 1/32nd-inch bit
  • 2 1/2-inch hole saw
  • Tape measure
  • Rubber gloves
  • Safety glasses
  • Zip ties
  • Lava rocks

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  1. 1

    Measure the height and length of your aquarium.

  2. 2

    Cut vinyl guttering to the length of your aquarium with a jigsaw.

  3. 3

    Stack vinyl guttering face down on your work surface until the height of your aquarium is reached.

  4. 4

    Drill evenly spaced holes into the sides of the vinyl guttering.

  5. 5

    Drill desired number and pattern of 2 ½-inch holes into the front of the vinyl guttering with a hole saw. These holes will serve as the entrances to the caves in the background.

  6. 6

    Attach vinyl guttering together by weaving the zip ties through the holes and closing zip ties securely.

  7. 7

    Put on rubber gloves and apply a thin layer of aquarium-safe silicone to the front of the vinyl guttering using a caulking gun.

  8. 8

    Apply a small amount of silicone to the back of each lava rock as you secure it to the vinyl guttering. Stack the lava rocks one row on top of the next until the entire front of the vinyl guttering is covered. Allow the silicone to dry completely.

  9. 9

    Drill holes across the top of the back of an acrylic aquarium or into the plastic frame of a glass tank.

  10. 10

    Place the background inside the aquarium. Secure it into position with zip ties by threading ties through the holes in the aquarium.

Tips and warnings

  • Add Java fern to your aquarium to reduce any rough surfaces on the lava rocks.
  • Always wear safety glasses when drilling.

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