Most live rock comes from areas close to natural reef habitats. It basically consists of dead and washed away coral, overgrown with a multitude of organisms. Highly porous with a larger surface than most filters can provide for, it became home to numerous organisms, plants, microbes, invertebrates and other animals living in and on the rock.
The purpose of live rock in marine tanks is to establish biological filtration (nitrification). This, and sometimes a protein skimmer, will meet all the filtration requirements for your aquarium.
Live rock, if freshly harvested, has actually too much living on it and a large number of those organisms can not survive the process of shipping and the whole transaction that is involved with it.
As a first step the rock has to be cured. "Cured" is a term that refers to the process of bringing the rock back to life and to create a healthy mix of species. The more species the better. But few species will dominate this habitat since many die off during the harvesting and transportation process.
Curing live rock starts by scraping off dead matter and organisms from the surface that would not survive. The rock is then placed back in a well-filtered tank where nature runs its course. During this time bacteria will settle and unwanted organisms will die off, while many species return to claim their habitat. Another term next to "cured" is "seeded". Seeded refers to live rock that has been cured and established. Seeded rock is what you usually buy at the pet store.
Live rock has to be submerged in water at all times. If you buy cured or seeded rock the shipping time should not exceed 24-36 hours. Dead matter has a foul smell, this will give you an indication if the rock is cured as claimed.
In any case, it is advisable to remove any dead matter from the rock before placing it into the tank and to continue doing this by siphoning until the rock is established. By not removing dead matter from the rock your aquarium will get heavily polluted.
The best way to implement live rock is by treating the rock as if it would have been neither seeded nor cured. While cleaning the rock, make sure it does not dry out. Remove everything that looks dead or weak, sponges and algae have to be removed, as they will not survive. A toothbrush comes in handy. At this time some animals might show themselves and can be removed. In most cases animals such as stone crabs, shrimps, and bristle worms are not desirable. Coralline algae on the other hand are beneficial for the system and should be left on the rock.
Place the rock in your tank after you have successfully cleaned and removed any unwanted matter and animals.
The rock is now ready to cycle. All the equipment you have installed should be running now. As mentioned above a protein skimmer is a good addition, but you should use the set-up that you feel comfortable with.
Cycling of the rock is about the same as cycling an aquarium. The bacteria will build colonies and ammonia and nitrite will spike resulting in nitrates. The animals, sponges etc. that you have removed before would not have survived this ordeal but would contribute to severe water pollution at this time. (See our article about fishless cycling, as this method can be used to speed up the process). Do not add fish before the cycle has been completed.
As indicated in the name, live rock will be the home for various species and microbes as well as bacteria. It will contribute to the overall bioload of the tank. Treat live rock as you would treat fish. Add one at a time and be aware that the tank has to adjust when new rock is added.
One method of avoiding pollution associated with new rock is to place the rock in an aerated bucket for one week prior to adding it to the tank. During this week excess nutrients will leach out. Keep the bucket covered in order to prevent algae growth caused by light.
Very important are the quantity and the set-up. Too little rock will result in insufficient bacteria colonies, which will make the biological filtration ineffective. Too much rock leads to dead areas.
Dead areas are spots covered by other rocks blocking light and water circulation. Waste particles in these areas are not broken down as it would be the case on the "living surface", nor can they be easily removed. This creates pollution in form of nutrients (nitrates)which will further diminish the water quality. Dying rock itself has the same effect.
Algone will control nutrient build up in this set-up and further balance the aquarium into a natural and healthy environment.
The correct amount of live rock is in-between 1.3 - 1.5 Lbs per Gallon of water. The minimum would be 1 Lb while never exceeding 1.75 Lbs. per Gallon.
Live rock is a great addition to any marine tank. Not only because of it's function, but also its looks.