How to Make Faux Aquarium Rocks

An aquarium can be more than a comfortable marine habitat, it can be your own personal underwater world. To that end, some people would prefer to decorate their marine landscape with rocks of their own creation. This is no quick and easy task, however. In the end, these creations are more than simple concrete slabs, but rocks forged with your own (well-protected) hands.

Things You'll Need

  • 3 quarts of Portland cement
  • 3 quarts of peat moss
  • 3 quarts of perlite or vermeculite
  • 1 quart of water
  • Safety gear (gloves, goggles, dust mask, etc.)
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Instructions

    • 1

      Don all your required safety gear; waterproof gloves, safety goggles, work clothes and especially a fine-particle dust mask.

    • 2

      Mix together the three ingredients well, in a large mixing container such as a wheelbarrow, Add water, slowly, and stir thoroughly into the mixture. Add only a little at a time, stirring each time.

    • 3

      Squeeze the mixture with your gloved hand, Ideally, the mixture should hold together, and secrete only a few drops of water. If this is not the case, add a fraction more water. Wait ten minutes, to let the water soak in. Add more water if the mixture seems too dry.

    • 4

      Form your rocks with the mixture. If you have a shape in mind, try creating a form to hold the mixture beforehand. Afterwards, let the rocks set.

    • 5

      Mist the rock thoroughly, and carefully place it in a black garbage of plastic bag. Seal or tie the bag airtight, and place it in direct sunlight to cure.

    • 6

      After 24 hours, open the bag and scratch the rock gently. If any of the rock comes off underneath your nail, re-seal the bag and let it sit for another period of 12 hours. Repeat as long as necessary. When you can no longer scratch off bits of the rock without significant effort, let the bag sit at room temperature for at least one week, or even up to a month or more.

    • 7

      Remove the rocks and soak them in fresh water for at least three days, changing the water daily. This is done to leach the lime from the rocks, so that it won`t damage your aquarium. Continue to wear gloves, as lime can burn the skin. Alternatively, set the rocks outside for one to two months, to leach naturally with rainfall.