Homemade Reef Rock

Mix together all reef rock ingredients in a 5 gallon bucket: 1 part aragonite sand; 4 parts crushed oyster shell; and 1 part Portland cement, white type II. Stir them around with your fingers until mixed together. Wear rubber gloves while you work with the rock mixture. Cement can cause skin irritation and burns.

Fill up half of a plastic storage container with argonite sand. This will be the mold. Add just a bit of water--enough to dampen the sand slightly--then form a mold of your preference. You can use your knuckles to create depressions in the sand or other objects to make unique shapes. Spread a few shells, crushed coral or oyster shells around the sand to add more decoration if you wish.

Scoop out enough of the dry rock mixture out of the 5 gallon bucket to fit into the half-full storage container, and place it in a separate 5 gallon bucket. You can use the remaining dry mixture later to form additional rocks if needed. Add water and stir until the mixture becomes slightly solidified. You should be able to grab the mixture and form it into a ball without the mixture dripping any water.

Place the rock mixture into the half-full storage container. Don't form the mixture into any shape, just gently place it into the storage container and slightly push it onto the sand. This will keep the rock looking natural and porous, like coral.

Sprinkle more shells or crushed coral over the rock mixture if you prefer, then cover it with a layer of argonite sand. Let the mixture dry for 24 hours in a cool place, then remove the mold and lightly rinse the mold to remove any loose surface sand.

Place the rock into a 5 gallon bucket and fill it with tap water until the rock mold is submerged. This will cure the mold and reduce the rock pH to a safe level for your aquarium. Change the water in the container twice a week for five weeks.

Drain the water in the container out completely after the fifth week. Test the pH level of your tap water with a pH test kit and record the pH value. Fill the container back up with water and let the rock sit in the water for one week without draining.

Test the pH level in the container after a week. If the pH level has risen from your recorded pH level, repeat the process for another week or until the pH level of the tap water and the water in the container are the same.