How to Make Artificial Living Coral Rocks

Written by carole ellis
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In order for a rock to be "live," it needs to be able to support bacteria, algae and other living organisms that would normally grow in an aquarium. Any fake rock can work in a similar manner to a live rock and eventually become "live" if it is porous enough to support these populations. All you need to do is add a few components to your regular rock recipe to make artificial living coral rocks for your aquarium.

Skill level:

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Things you need

  • Large plastic tub
  • Sand
  • Portland cement
  • Elbow macaroni
  • Two 5-gallon buckets
  • Rubber gloves

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  1. 1

    Fill the plastic tub with damp sand. You will make your coral rock moulds out of the sand. Once the sand is packed in tightly, dig out areas for the coral rocks. You can make them in any shape and size you want. For coral, you might add a lot of branches or refer to a picture of coral to make your shapes more realistic.

  2. 2

    Mix up your cement. Put on your rubber gloves at this point and leave them on. To start, simply add water to the cement. The exact amount of water will vary depending on the brand you use, so check the package for precise measurements. The result will be a thin mixture. Add sand and elbow macaroni in a 1:1 ratio until the cement can be moulded with your hands.

  3. 3

    Push the cement-sand-macaroni mixture into the sand moulds you created. It is OK if it does not fit entirely smoothly since some of the macaroni may poke out. Just make sure that the end result is a shape you like.

  4. 4

    Let the cement set. Depending on the brand, this may take several hours or several days. The cement should be completely hard before you move on. Keep it in a warm, dry place while it is setting.

  5. 5

    Rinse off the sand. When you remove the fake living coral rocks from the sand, you can run them under water to get extra sand off them. When they are clean, you are almost done.

  6. 6

    Cure your artificial living rocks. Place them in a bucket of water, making sure they are completely submerged. Change the water daily for six weeks. At the end of this time, they should not impact the pH of your tank and you will be able to safely install them in your aquarium.

Tips and warnings

  • Oyster shells also work in place of elbow macaroni.
  • Some hobbyists express concern about Portland cement having aluminium in it. While most agree that there is such a low concentration that they have seen no ill effects, if you have especially sensitive fish you might want to purchase a cement that does not contain aluminium.

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