Natural river rocks are beautiful and can add ambiance to your aquarium or terrarium—best of all, they're free. Unfortunately, they can also be home to creatures, bacteria and other germs that may be harmful to your reptile or fish. You can use natural river rocks but it will be necessary to properly sanitize them before use. Some rocks may not be suitable for use in your aquarium, so check with your local dealer for a list of rocks to avoid adding to your tank. It takes a number of days to properly clean river rocks before they will be ready for use, so be sure to plan ahead.
Scrub river rocks with a stiff-bristled brush and 1 tbsp. of antibacterial soap added to warm water, taking special care to get into nooks and crannies.
Rinse the rocks with plain water and soak overnight in non-iodized salt water--1 cup of sea salt to every gallon of water.
Remove the rocks from the salt water the following day and rinse.
Prepare a bleach solution of 1 part bleach to 10 parts water. Scrub the rocks' surfaces and allow the rocks to sit in solution for 30 minutes. Rinse with plain water.
Place the rocks in an aluminum, non-coated pot and fill with water.
Bring water to a full boil and allow the rocks to boil for 30 minutes to sanitize and remove any remaining bleach residue. Use extreme caution when boiling rocks, as there may be gas pockets prone to explosion. If the rocks are craggy instead of smooth, you may prefer to pour boiling water directly over the rocks instead of boiling them on the stove.
Rinse the rocks with clean water and soak for 24 hours in plain tap water before adding to the aquarium or terrarium.