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What is Live Rock?

Live Rock in Aquarium

its all about the rock!

What is Live Rock?

The first decision you will have to make when setting up a reef tank is the type of rock you will use for your aquascape.

Real Reef Live Rock

Real Reef

A popular choice for most hobbyists now is using a manmade type of rock instead of wild collected live rock. Our favorite brand of man made rock is Real Reef which is made in the US of natural dry reef ingredients and does not require curing and may be added to any reef tank without concern. It contains environmentally and reef safe dyes that simulate natural coralline algae colors and is made from totally natural reef ingredients. We have used Real Reef rock for years with great success. The manufacturers of Real Reef are leaders in the industry and have quality checked their product extensively.

Wild Rock

Wild Rock

Wild collected rock has more variety of shapes and a greater diversity of life, but must be cured in a separate tank prior to adding to an established reef aquarium otherwise you will create very high nutrient levels in your main tank and likely kill much of your livestock and create severe bacterial and algae blooms. 

The trend in the hobby is going away from wild rock due to conservation issues and ease of use. 

Dry Rock

Dry Rock

Dry natural reef rock is also available and some folks like using it to create their reef structure. This is rock collected just the same as the wild live rock, but is subsequently completely cleaned and dried and has a bleached white appearance.  It is not live and does not contain any bacteria or have any coralline algae or any critters. Over time it will allow for colonization of bacteria, but does not have the diversity of life or color you can obtain from wild collected natural live rock that has all sorts of critters deep inside and is loaded with lots of beneficial bacteria needed to provide biological filtration for your reef.

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.

Nitrogen Cycle

nitrogen cycle

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.

Water Quality

Purified Freshwater is a Must!

Before we get into the discussion about curing your live rock, a word about freshwater. Obviously freshwater is the basis for our tanks, we add salt mix to this freshwater to create our reef tank's saltwater and we add freshwater to the tank daily to make up for water lost from evaporation. Purified freshwater is critical to the long-term success of your reef tank. You must eliminate any nutrients from your source of freshwater prior to using it for your reef tank. Otherwise, every time you use that impure freshwater you are adding nutrients in the form of silicates, phosphates, nitrates, etc. to your tank. These nutrients are food for algae. At least 95% of the time when folks call to discuss algae problems we find that their freshwater is to blame and not something going on in their tanks.  Please reference our Water Quality section for more information

Box of Live Rock

Step 1

OK, you got the box of rock, now what?

First, get a large tub of saltwater and have it ready when you unpack the rock, you may also want a second empty tub to be able to put the rock in after you dip each piece in this saltwater. In this first tub you can either have regular salinity saltwater with a specific gravity of about 1.025 or a higher salinity with a specific gravity of about 1.035. The higher salinity dip is used by some folks as a method of removing unwanted pests deep inside the crevices of the rock. Mantis shrimp for example will often crawl out of the rock when placed for a minute or two in the higher salinity dip.

Usually Live Rock from the Pacific does not have Mantis shrimp, nor many other forms of higher marine life that survive the trip to the US. This rock is not dead---far from it, just that higher forms of marine life such as crabs and shrimp often crawl out of the rock during transit and dry up and die, some remain deep inside the rock and are alive along with many worms and of course all the billions of bacteria inside and on the surfaces of the rock are still very much alive.

Live Rock

Step 2

Inspect Each Piece of Rock

Remove each piece of rock individually from the box and add it to this tub of saltwater. When you do so you will want to first examine each piece of rock and remove any obviously dead sponge or other decaying material. You can do this by hand or with a toothbrush or small scrubbing brush, a small flathead screwdriver is also handy for removing some types of decaying material from the rock. Once you have removed any dead and decaying material then place the piece of rock in the tub of saltwater and swirl it around to remove and dislodged any loose material. UNDER NO CIRCUMSTANCES SHOULD YOU SCRUB THE ENTIRE ROCK. This would remove many beneficial organisms such as coralline algae and bacteria. In this step we are simply trying to remove larger pieces of obviously dead and decaying material, we are not trying to scrub or "clean" the rock.

If you have a new tank you can cure the rock in your tank but it is best to do it in a separate tank or large plastic trash can. The rock can then be placed in your tank or in a holding vat to start the curing process until you get all the pieces examined.

Foam During Curing Process

Step 3

Good Skimming is Essential

The curing process will take about 2-4 weeks to complete. The curing process will eliminate any embedded material, but you need lots of water flow and a means of exporting this decaying material from the water. So, lots of water flow around and through the rock and a good skimmer to remove the dislodged material is imperative. The water flow can be created with a larger external pump so that its flow is directed over and through the rock or can be accomplished with several powerheads or other submersible pumps. Be sure to have more flow than you think you need and occasionally use a powerhead or turkey baster to "blow" around all exposed surfaces of the rock.

The rock may have a strong smell for the first 3-4 days, but with a good skimmer and a close initial inspection of each piece of rock and removal of obviously dead material should lessen this situation. In the first few days you will need to closely monitor your skimmer because the initial load of material and nutrients in the water with the addition of all the rock will cause the skimmer to foam excessively. After the first few days the skimmer should stabilize and less monitoring will be needed. Be certain that you have plenty of reserve for the waste the skimmer will be producing during these first few days.

Water Changes

Basically, the curing process is now set. It is just a matter of time until the rock is fully cured. Depending upon the amount of matter on the rock and the water flow and skimmer you have, the process will take about 2 to 4 weeks. You can also reduce the nutrient levels in the curing water and lessen the curing time by having more water flow and a bigger, more efficient skimmer and by changing a portion of the water in the tank or curing container. A schedule of changing 25%-50% of the water every week is usually best, but you can alter this according to how clean the rock is as you cure the rock. Many folks do minimal water changes and still cure their rock rapidly, but this can only be accomplished if you have other means of waste removal such as a good skimmer. The amount and frequency of water changes are something that will be different for every tank and system so you must determine when you will need to do water charges, some water changing is probably needed but you don't need to be excessive. Remember to use pure freshwater when mixing your salt water for the water changes otherwise you are just adding more nutrients to the system and the water change is useless. During the curing process you will also need to add purified freshwater to keep up with any evaporation to keep a constant salinity level in the tank or curing container water, your water's specific gravity should be about 1.025-1.027.

Things to Check:

Keeping the Coraline Going
You Must Supplement and Test

All the pretty colors of coralline algae on your rock can be kept alive if you follow some basic rules. Don't use too much light at the beginning and keep the water as pure as possible by having lots of water flow and a good skimmer, and use only purified freshwater for top offs and water changes. Do some water changes as you determine they are needed for your system, and supplement your tank to keep calcium and alkalinity levels at normal reef tank levels from day one and monitor this regularly. In tanks smaller than about 75 gallons the very best method of supplementation is with one of the 2-part liquid calcium and alkalinity supplements. These are balanced products and no other supplements are advised or needed when using these products. There are several on the market, I have used and been happy with B-Ionic from ESV Co. Be careful not to use other cheaper brands they are not as good and you will need a lot more daily. These 2-part supplements can be purchased in large quantities, as large as 8-gallon buckets, and the larger sizes are very economical on a per dose basis. You should use them daily, not every 3 days as may be indicated wrongly on the labels. Small daily additions will keep your tank's water parameters very consistent, dosing every 3 days as suggested on the product labels will cause a see-saw effect of calcium and alkalinity levels that is detrimental to marine life. To determine the amount needed to dose daily you must test your tank's water daily at first and then spot check weekly. We recommend using Salifert brand test kits, they are inexpensive, accurate, and easy to use. Test daily for calcium and alkalinity to determine your dosage amount and then check weekly and fine tune your dosage as needed. If one parameter is off then just add more or less of that part for a day or two to adjust the tank's overall levels. From the day your reef tank is set up you should strive for a calcium level of 450, magnesium level of about 1350 or higher, and alkalinity of 3.5-4.5 mq/L, 8 to 9 dKH. To check pH you should use an electronic pH monitor such as the Pinpoint brand monitor and it should be calibrated at least monthly, pH test kits are very unreliable and should not be used. If you use the 2-part supplements and have proper alkalinity and calcium levels then your pH will fall into place at about 8.2-8.4, there will naturally be a bit of a swing in pH levels from day to evening and this is OK if the pH does not drop below 7.8 or climb above 8.6.

If you have a larger tank or one that you plan on keeping large amounts of clams and hard corals you may need to use a calcium reactor because the number of 2-part supplements may become cost prohibitive in large tanks. For a new hobbyist and someone with a tank of about 75 gallons or less the 2-part supplements are the best at easily and inexpensively keeping all water parameters correct. The worse way of keeping these parameters in line would be to try to use separate supplements for each parameter such as different buffers, strontium, iodine, and other such additives. Adding all these separate supplements is a sure way to get everything out of whack, spend tons of money, be thoroughly confused, and then have a tank totally out of balance. Also, other miracle in-the-bottle supplements do not work, do not waste your money on any so-called "DNA" products or such other hype, it is not needed, resist the urge to think that a miracle in a bottle potion will help your tank despite what the labels say. Remember, good things take some time to develop and they will if you have patience with your reef tank. Do not add anything to your tank that does not have a clear and complete label of ingredients and for which you do not have a specific reason to add. Resist the natural human urge of thinking there is a short cut to success and it comes in a bottle with a fancy name or label.

Live Rock in Curing Tank


As the rock cures you should have minimal to moderate light on the rock. Too much light at the beginning will cause more ugly nuisance algae to grow in this nutrient rich environment and will also cause the coralline algae to fade and die, coralline algae do not like intense light. During curing, it is recommended that you use only LED lighting, preferably only blue light, with a daily duration of 2-4 hours during the first couple of weeks of curing and then slowly ramp up to the full photoperiod of about 8-12 hours a day with all lights. Do not cure the rock with metal halides, this may result in lots of nuisance algae and a rapid die off of the coralline algae. We once had a customer call that their rock was almost completely bare within 2 weeks even though he had a good skimmer and lots of water flow and proper calcium and alkalinity levels, well it turned out he had used several metal halide lamps to illuminate his tank from day one to cure the rock. Coralline algae grow best in lower light areas. After being transported from the South Pacific dry and then exposed to intense light the coralline algae will fade and die. So, again, use only low light levels for the first couple, you must have some light for the coralline algae to survive, but not too much.

algae blooms

Inevitably in this nutrient rich environment during the curing of your rock you will have some nuisance algae blooms. This is normal and natural and can be managed before you develop an algae nightmare. Follow the instructions in this guide and the algae blooms will be minimal and short lived. Within the first few days through the first 2 weeks you may see brown diatoms grow on the rock that look like a brown fuzz. This will normally die off within a week or so and may be followed by growth of some green algae. This will also die off soon and if you do not add a bunch of other life to the tank during this time then the curing process should be completed within 4 weeks. It is best to wait until the initial ammonia is gone before adding any invertebrates such as a "clean up" crew. It is best to add these animals after 2-3 weeks of curing because many will not survive in the high nutrient environment present in the water during the first couple of weeks of curing. When adding inverts keep them to a minimum at first and use mostly snails to help control algae. Adding a lot of inverts early may result in many dead inverts when the food supply in the form of algae naturally dies back later in the curing process.

Coraline Algae on Rock

You Now Have Cured Rock

After 2-4 weeks your rock should be cured and you will then see more coralline algae growing on the rock and elsewhere in your tank. Soon you will have multicolored coralline algae growing everywhere and once you begin to add fish and corals you will have a fantastic reef tank. Once the ammonia and other nutrients are lower in the tank as the bacteria population establishes you may add some invertebrates to assist in nuisance algae control and to scavenge for leftover food. Slowly begin to add fish to the system to further complete the cycling process. Once all diatoms and nuisance algae blooms are finished and you have a good growth of desirable coralline algae then add some corals. If you are patient and follow these basic guidelines you should have a great reef tank within a few months.


Aquascaping Live Rock

If you cured your rock in a separate container from your main tank then you will need to arrange the rock in what is called your aquascape. This can be done on the floor (covered with a drop cloth of course) or in the tank itself. You will note that as you examine the rock that some pieces will have more coralline algae color than others and that one side may have more than another. This is normal and over the next 4-6 months in your tank, with proper conditions, all the coralline algae will grow and cover all the rock, so don't be too concerned with color at this point.

As you set up the rocks into a reef structure you like, move the pieces around a bit. One piece may look OK on its side, but maybe try it on one end or turned a different way and then it looks GREAT. It takes a bit of time and experience to aquascape well, but there are no right ways or wrong ways, it is all about what you think looks good and if you are satisfied then it is right. Try to leave some open spaces for fish to swim through and allow for good water flow through the rock. If you decide to use sand in your tank I prefer to place the rock directly on the sand, this gives the most stable structure. A bed of about 1 to 2 inch depth of dry fine grain Aragonite sand may be placed in the tank before you add the rock, live sand should only be added a few weeks after the curing process begins since the critters in the sand bed need food and you will not be adding any for a while, of course they also feed on the decaying material from the rock, but it is best to wait until the ammonia levels drop a bit before adding lots of live sand. When adding live sand, it should be added directly to the top of the original sand bed and not mixed in, worms and other critters in the sand can be damaged if over handled and they will work their way through the sand on their own. Worms and other small animals in the sand are beneficial in keeping the sand bed alive and healthy and should not be disturbed or removed, never vacuum your sand bed or disturb it in any way. Mixing or stirring the sand bed will add oxygen to the sand and destroy the vital anaerobic bacteria deeper in the sand bed, these bacteria are very important to the health of your tank. Bacteria, worms, and other critters are added to the sand bed from your live rock, many are living deep inside the rock, and when you add live sand to the sand bed you will add lots of life.