Live Rock

live rock

Choosing from a vat of cured live rock

What Is Live Rock?

Live rock is natural rock from the reef that comes festooned with a diverse array of living organisms such as coralline algae, sponges, tunicates, featherdusters and other tiny worms (or a large worm if you’re not careful with your selection).  It is this bio-diversity that makes otherwise inanimate rock, live.

More importantly, aquarium live rock harbors populations of nitrifying and denitrifying bacteria, which enable ammonia to be converted to harmless nitrogen gas. As discussed on our page on the Nitrogen Cycle, live rock is the foundation of the biological filter in saltwater aquariums.

Fiji Live Rock

Quality Fiji Live Rock

The Difference Between Cured and Uncured Live Rock

Cured live rock possesses no unpleasant odors — it smells of the sea, or perhaps the freshest of seafoods. Cured live rock can be placed directly into an established aquarium, and because of the biodiversity it offers, it will be of benefit to the tank inhabitants by way of edible micro organisms, while giving a boost to the bacterial populations in the aquarium

If the rock smells vaguely like decomposing fish, it is uncured live rock that has spent too much out of water.

Uncured live rock has an unpleasant smell because of organisms that have died off on the surface and within the rock. If uncured live rock is placed into an established aquarium, it will release ammonia, nitrates and phosphates, elevating these levels in the aquarium.

There sometimes isn’t much difference in the appearance of cured, semi-cured or uncured live rock, so smell would still be the best indicator.  But when in doubt, follow the instructions coming up and cure it!

Curing Live Rock

Live rock is best cured in a vat or plastic tub. The tub should be filled with either newly made saltwater, or aquarium water removed during a waterchange.

live rock

Cured live rock in vats at an LFS

But before we begin curing, it is a good idea to go over the rock with a plastic brush to remove any dead organisms, sponges and slimy, white film on the surface. Rubber gloves are highly recommended!

Aqua Gloves by Coralife are a necessary accessory for every saltwater aquarium keeper — it keeps your arms and hands dry, and protects against stinging corals and potentially hazardous coral toxins emitted by zooanthids and palythoa polyps. It also eliminates any possibility of detergents, soaps, gels or lotions from your hands from ever entering your aquarium!

Rinse Live Rock In Seawater Or Aquarium Saltwater Only!

The rock should then be thoroughly rinsed in seawater or aquarium saltwater only. Rinsing it in freshwater or tapwater will only kill off beneficial bacteria and other useful microorganisms.

Ready To Cure

Transferring the rock to our tub full of saltwater, ensure that the rock is fully submerged. Since it will take a good two to four weeks for the rock to be properly cured, it is best if the tub or vat is situated in a place where it can remain undisturbed for that period of time, and away from direct sunlight.

The live rock will start to smell during the curing process, which is a good reason for keeping it away from your main living area!

Keep the water temperature at around 80 degrees F (or plus or minus 4 degrees F either way) and circulate the water vigorously with one or more powerheads. If a spare protein skimmer is available, go ahead and hook it up. You will be surprised at the amount of gunk it will pull out of a tub full of curing rock.  Detritus that settles on the bottom of the tub should be siphoned out from time to time during the curing process.

30% of the water should be changed every three days until the rock smells fresh.  Ammonia and nitrite readings of the water in the tub should remain at zero.  If ammonia appears, it will kill off beneficial bacteria and any organisms still alive on the rock.  If ammonia does appear, change enough of the water for it to go back down to zero on the test kit.  From my experience, the 30% water change regimen mentioned should take care of any ammonia or nitrite that might appear.  Test to be sure!

When adding newly cured live rock into an established aquarium, it is best to perform a final sniff test.  If the rock smells even vaguely of decomposition — some will say rotten eggs — the rock is not ready and should be cured some more.

Once fully cured, add only a couple of pieces of rock at a time over a period of several days.  Monitor and test the water in the aquarium for ammonia, nitrite and nitrate.

Links to more Saltwater Aquarium Filtration Pages:


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