Live, or living rock (LR) is basically parts of the coral reef that have been broken off during storms etc. It has laid on the sea bed for weeks, months or even years and during that time, it has been colonised with litterally millions of animals ranging from microscopic bacteria to larger copepods and amphipods to even larger shrimps, crabs, lobsters etc. LR is very porous and lightweight. This allows many of the small animals (critters) to colonise deep into the rock and remain free from predation.
Once LR is collected, it is shipped by air in a moist state in sealed bags or boxes (if it were shipped wet, the cost would rocket because of the weight). During the shipping process, many of the higher life forms die off due to lack of water. However, the little pores remain wet and the smaller life forms survive the journey.
Once it reaches the dealer, it has to then be cured. This is a very costly and long process which involves putting the LR in large vats of saltwater and running large protein skimmers. The reason for this is that a lot of the dead critters start to rot and if placed directly into your tank, will cause unacceptable ammonia levels and probably kill most of your tank inhabitants. The LR is scrubbed and new saltwater added regularly. This whole curing process can take a month. The LR is then placed into large vats of mature saltwater where it is now ready for sale (at a cost of around £200 for 20KG's)
Once the rock is placed into your tank, the fun then starts. Within a few weeks, many life forms that had remained dormant, start to grow. This can include small corals, decorative algea, polyps and mushrooms. Even after years of it being in the tank, new things can still spring up.
Many reef keepers use LR as filtration. The tiny pores that contain the bacteria are a superb way of filtering the reef. They contain both aerobic and anaerobic bacteria which reduces nitrites and nitrates respectively.. However good water flow around the rock is essential to keep the bacteria fed.
Among the beaties that are found on the rock, there are also some that are not so welcome. Some large, destructive crabs, shrimps and lobsters etc can be imported as tiny specimens and survive the journey. Being nocturnal, the first time you know you've got them is when you see your prize coral being munched away or your lovely colony of Neon Gobies slowly disappearing one by one. This is a rare occurance though and should not put anyone off. It has even been known for a fertilised moray eel egg to be imported and hatch in the tank !!!.
LR is imported from all over the tropical world but rock from Fiji is usually the lightest and best although rock from the Caribbean is also good. People are starting to now create LR nurseries, where porous rocks are being put into the sea and left to colonise for a year or two. This ensures that our reefs are not exploited for the aquarium trade and also ensures we will have a never ending supply of LR.
It still amazes me the amount of life that comes from the rocks and continues to grow, multiply and increase the bio-diversity of the reef tank.
Other porous rock such as tufa and homemade rocks will quickly become "live" if added to a tank full of existing LR as the bacteria and critters will soon colonize that too.
I hope this explains the wonders of LR.
this is not my article but i asked permission off the writer, it was written by Andy Jeavons
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I have set up my first marine tank with 2 external filters and I am going to put 20kg of live rock in the tank to begin with. I would like a fish only system to start, but I would like to develop this in the future.Is this a good way to start?
imblindio, I have been quoted at least 1kg per 10 litres, but I think this is if the live rock is as your main filtation system and is an absolute minimum. I am new to this though, so you may get better advice