How to Know the Difference Between Good and Bad Live Rocks for Saltwater Aquariums

Live rocks are pieces of coral that broke off naturally from the reef. They are then sold as biological filters for saltwater aquariums. Because they still contain bacteria, they break down fish waste and uneaten food, turning it into harmless nitrogen gas that escapes to the surface. To decide whether live rock is good or bad, you need to know where it is from, if it has been cured, and if it is natural or not.

  1. Source

    • Ask the retailer to tell you about the origin of the rock. The best live rock is sourced from the Pacific Ocean. It tends to be porous, which gives the rock a larger surface area to interact with the water. Atlantic Rock, Gulf Rock, and Caribbean Rock will work, but base rock will not be as effective. Base rock comes from the bottom of the reef where sunlight is minimal, which means fewer organisms have grown on it.

    Shape

    • The best live rock will have a complex shape with many crevasses and pores. In addition to providing hiding and exploration places for the fish, these crevasses increase the overall surface area of the rock. This gives bacteria and other tiny organisms more room to grow, which in turn makes the rock a more effective filter. Rocks with unusual or interesting shapes also tend to be more attractive than smooth-shaped rocks..

    Cured

    • You will have the option to buy rock "cured" or "uncured." Curing scrubs off the dead and dying organisms so their decomposition does not upset the balance of a tank. The rock then needs to be treated for almost a month. Uncured rock is much cheaper, but curing it at home is a smelly and long process. It requires ammonia, a dark, empty and heated tank with a power head to keep the water moving, and a protein skimmer to remove the discharge from the rock. You also need to change the water regularly.

    Artificial

    • Artificial live rock is not necessarily better or worse for a fish tank, but it is better for the coral environments. In a process called "aquaculturing," a regular porous rock is placed in the ocean and left so organisms and bacteria can grow on it. Months later it is harvested and sold as live rock. Because it is not taken from a reef, this is the most sustainable source of live rock. Your retailer will be able to tell you if a live rock has been sourced in this way, but still consider its shape and whether it has been cured before making a decision.