What Kind of Rocks to Use in Salt Water Aquariums?

Live rock is essential for use in saltwater aquariums because it acts as a natural filter. The rock's surface area enables beneficial bacteria and invertebrates to hide and live in it, cleaning and filtering the water. Live rock is harvested from the ocean after it has broken off coral reef structures because of tropical storms and hurricanes. It is called "live rock" because it contains tiny living organisms such as beneficial saltwater bacteria, algae, marine worms and crabs.

  1. Benefits

    • Your ability to successfully maintain a saltwater aquarium is dependent upon your use of live rocks because their main purpose is to act as a biological filter. They provide substantial benefits related to growing beneficial bacteria in your aquarium. The good bacteria produced by live rock converts ammonia from uneaten food and waste to nitrite, and nitrite to nitrate. This is called the nitrogen cycle, and maintaining its balance is critical in keeping tropical saltwater fish and reef aquariums.

    Characteristics

    • Live rock is highly porous, enabling living organisms, fish and small invertebrates to make their home within its many grooves and holes. Your saltwater fish will also use the rock for hiding and food. Live rock is beautiful and decorative. It changes constantly and will grow beautiful pink and purple coralline algae, as well as a variety of new and interesting organisms.

    Cured and Uncured Live Rock

    • Cured live rock is cleaned to remove dead organisms and placed in a high-circulation curing tank by the retailer for several weeks before being sold. Cured rock is expensive but easier to set up because it requires no preparation before use. Uncured live rock is generally one-third of the price of cured rock, but must be carefully scrubbed and cured before placed in your aquarium. Curing takes time, is dirty and the odor from the dying organisms can be overwhelming.

    Types of Live Rock

    • Aqua cultured rock is a porous-type rock that has purposely been placed in the ocean for several years, encouraging organisms and bacteria to populate it. Atlantic rock, Caribbean rock and Gulf rock are taken from their respective regions, and are not as porous as other live rocks. Base rock is found under larger coral reefs and contains the least amount of living organisms, making it the least expensive. Pacific rock is collected from Indonesia, Fiji and the Marshall Islands. It is the most porous of all live rocks and contains the most beneficial bacteria and living organisms, making it the most expensive.

    Care and Use

    • How effective the live rock is in your aquarium depends on how much you use. Use 1 lb. of rock per gallon for aquariums that contain only fish, and at least 2 lb. per gallon for reef aquariums (mainly live corals and other marine invertebrates, including fish). Monitor the nitrite and nitrate levels of your water, ensuring the readings are within a satisfactory range. Performing periodic water changes might be necessary in the beginning to establish healthy nitrate levels.

    Where to Buy

    • Live rock can be purchased from retail aquarium shops in coastal areas and from aquatic shops that supply saltwater tanks, fish and accessories. It can be costly because of the labor costs involved in supplying it. The rock must be harvested from the ocean by divers, cured by retailers and shipped to aquatic shops. Consult with a retailer that specializes in saltwater aquariums. Depending on the amount and types of fish you plan to keep, a retailer might suggest using a protein skimmer along with your live rock to maintain a healthy water balance.