Why do we cure?
Understanding Live Rock and How to Cure It
Live rock is comprised of ancient calcium carbonate coral skeletons collected near natural reefs in the Pacific or Atlantic Oceans and it serves as the base for your reef tank. Usually the rock is collected in shallow waters near reefs and is generally about softball to basketball in size with a wide variety of unique shapes including branches, shelves, and many assorted gnarled configurations. Live rock has lots of forms of sea life growing on and inside it including sponges. Larger bits of macro algae and sponge are removed from the rock before it is packed and shipped from its origin. However, some sponges and other life on and in the rock remain and die off during processing and shipping and this die off must be removed from the rock before it is added to your aquarium otherwise the rotting matter will skyrocket the ammonia and other nutrient levels in your tank likely killing all your tank inhabitants. “Curing” is the process that is used to cleanse the rock of this dead and decaying material and thus allows it to be safely placed in a new or existing reef. The curing process usually takes about 3-4 weeks and can be accomplished in a separate aquarium or a large plastic trash can or other vessel.
Dead or Alive?
Wild collected live rock has likely been collected many days to weeks before it is ever exported to the US and once in the US it may sit for many days or weeks before you receive it. This is the normal process unless you buy cultured rock that is terrestrial rock that has been put into the ocean, usually from Florida, and allowed to encrust with different sea life--usually this type of rock is shipped fresh from the ocean but this type of rock is very dense, lacks unique shapes, and always has bad hitchhikers that can destroy much of your desirable reef inhabitants. For the sake of our discussion here we will assume you are curing live rock obtained from some Pacific location such as Indonesia--this is very nice rock with very unique shapes and it is lightweight and easy to cure! Often shipping live rock can also be delayed up to 48 hours or more. Despite all these delays and what seems like a very long process, your live rock is very much alive even if it has been sitting in the box for many weeks. We have obtained boxes of live rock from Indonesia and saved them for tank builds we do and opened boxes weeks after receiving them and many crabs and other life is still alive plus all the beneficial bacteria are certainly alive on and deep inside the rock. It may take a bit longer to cure, but much of the life is still alive deep inside the rock. Some coralline algae may die off in the initial curing process, but within a few months all the coralline and color will regrow. Follow the curing guidelines described on this page and your rock will serve as an excellent base for your captive reef.
When you purchase Live Rock it needs to be "cured" before putting it into an established tank with fish and corals. Live rock originating from the the Pacific is shipped dry. Many simple forms of life growing on the rock such as sponges will die when exposed to air during the transit of the rock to the US. All rock originating from the Pacific is shipped dry with some moist newspaper on top to keep it damp, it is not shipped submerged in water as this would make the rock cost prohibitive due to excessive freight costs, and that is not needed to preserve all life on and inside the rock.
"Curing" is the process of eliminating any dead and decaying material from the rock. This material will initially generate high levels of ammonia in your tank and this is toxic to many higher forms of marine life such as fish and corals. So, putting uncured live rock into an established reef tank with fish and corals can be disastrous. Uncured rock may be cured in a separate container or tank or may be cured directly in your reef tank if it is a new set up without any other animals in the system.
Bacteria and the Nitrogen Cycle
Dead and decaying material, fish waste, and left-over food will all produce ammonia in an aquarium, ammonia is very toxic to most forms of marine life.
In a process called the Nitrogen Cycle, bacteria will utilize the ammonia and produce nitrites which is still toxic but less so than ammonia. The bacteria that utilize ammonia do so in an environment with oxygen and are called aerobic bacteria. Aerobic bacteria also utilize nitrites and produce less toxic nitrate. Other bacteria that only live in an environment without oxygen, anaerobic bacteria, will utilize the nitrate and reduce it to nitrogen gas that can safely be emitted from the tank in the form of tiny nitrogen bubbles. Again, ammonia and nitrite are very toxic to most marine life, nitrate is much less toxic. However, these forms of nitrogen are used by algae as food. This algae may be in the form of ugly nuisance algae that overruns your reef tank and turns your relaxing hobby into an eyesore that is a chore to constantly clean, so you will want to eliminate as much nitrogen waste in your reef tank as possible. To measure the water levels of ammonia, nitrite, and nitrate use Salifert brand test kits. They are accurate, inexpensive, and easy to use. These test kits are available from most online reef related dry goods suppliers. To test for pH, you should use an electronic pH monitor because all saltwater pH test kits are inaccurate and the results are unreliable. Get a Pinpoint brand pH monitor and keep it calibrated for the best pH monitoring, these are also available from most dry goods dealers for about $100.
A Reef Aquarium Is All About Balance
The key to running a successful and nuisance algae free reef tank is balancing the wastes (ammonia leading to nitrite then nitrate) produced by the inhabitants in the tank and nutrients added to the tank in the forms of impure freshwater and food balanced with nutrient and waste exports it is a critical balancing act that can mean the difference between live or dead fish and corals or a beautiful reef and one overgrown by algae. The goal is to remove as much waste as possible and then rapidly reduce any remaining wastes into nitrogen gas and have it emitted from the tank. To do this you must balance the amount of animal waste and food or other nutrients added to the tank with the amount of waste and nutrients taken out of the tank. To do this most folks use several means of nutrient removal.
A good protein skimmer can remove some waste, a sand bed can harbor aerobic and anaerobic bacteria that break down wastes including nitrates into nitrogen gas but a sandbed can also become a nutrient sink, water changes can remove some nutrients and waste and dilute the amounts of remaining waste, algae utilize waste as food this can be in the form of ugly nuisance algae growing in your main tank or as intentionally kept macro algae in a separate refugium that grows and uses wastes as food. Cured live rock also has anaerobic bacteria deep inside and aerobic bacteria on its surface and these bacteria drive the nitrogen cycle that turns waste to ammonia, then nitrite, then nitrate, and eventually nitrogen gas. Good quality cured live rock is the foundation for your reef tank's waste management system, and the support structure on which corals will be placed.