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Curing Live Rock

As with many things related to your reef aquarium, curing live rock may seem complicated and mysterious for the new hobbyist. Well, curing live rock, as with all other things related to your reef, is not difficult once you know a few basic guidelines. Hopefully the following information will help answer your questions and guide you through the process.  If you should have any questions do not hesitate to call Dr. Mac toll-free 877-887-5224.

Is My Live Rock Dead?

Box of Live Rock on Arrival Often shipping live rock involves using air freight services provided by many airlines and this service often can be delayed up to 48 hours or more. Live rock is very much alive even if the rock is sitting in the box for a few days. 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.

What is Curing?

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 South Pacific islands such as Fiji and Tonga 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 South 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 besides, it 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 disasterous. 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, 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, all of 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.

It's 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 unpure 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 nutritent 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, 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 alage growing in your main tank or as intentionally kept macro algae in a seperate 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 also the support structure on which corals will be placed.


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

OK, you get 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 South 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.

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!! The rock can then be placed in your tank or in a holding vat until you get all the pieces examined.


Once you have examined and dipped each piece of rock then you can begin to arrange the rock into some type of reef structure. 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 also to allow for good water flow through the rock. I prefer to place the rock directly on the sand, this gives the most stable structure. A bed of 2-4 inches 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 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 orginal 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 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 vacume 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 also when you add live sand to the sand bed you will add lots of life.


The curing process will take about 2-4 weeks to complete. You may get a piece of rock that just smells nasty, and likely this piece has some type of dead or dieing coral on it. The initial examination phase should help to remove this, but if may be deep inside. The curing process will elimiate this material, but you need lots of water flow and a means of exporting this decaying material from the water. So, to properly cure your rock you must have lots of water flow around and through the rock and a good skimmer to remove the dislodged material. The water flow can be created with a larger external pump so that it's flow is directed over and through the rock or can be accomplished with several powerheads or other submersible pumps. What ever you use, be sure to have more flow than you think you need and ocassionally 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 stablize 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.

Are Water Changes Needed?

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 effecient 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 your results 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 really good skimmer. The amount and frequency of water changes are something that will be different for every tank and system so you must determine if and 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 water 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.

Should I Give the Rock Light?

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!! It is recommended that you use only fluorescent light, preferably only blue actinic light, with a daily duration of 4-6 hours during the first couple of weeks of curing and then slowly ramp up to the full photoperiod of about 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 to moderate light levels for the first couple of weeks actinic flourescent lamps are best to use, you must have some light for the coralline algae to survive, but not too much.

Algae Blooms are Inevitable in the Beginnning

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 as long as 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 surive 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 and 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.

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 use only actinic fluorescent lamps for a few hours a day, 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. or CalxMax from Warner Marine Research (persionally I like this brand the best, it uses the most pure raw ingredients). Be careful not to use other cheaper brands they are not as good and you will need a lot more on a daily basis. 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 on a daily basis, 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 on a daily basis 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 detemine 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 400-450, magnesium level of about 1300, and alkalinity of 3.5-4.5 meq/L. 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 you pH will likley 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 as long as the pH does not drop below about 7.8 or climb above about 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 amount of 2-part supplements may become cost prohibitive in large tanks. For a new hobbysist 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 seperate supplements for each parameter such as different buffers, strontium, iodine, and other such additives. Adding all these seperate supplements is a sure way to get everything out of whack, spend tons of money, be thourghly confused, and then have a tank totally out of balance. Also, other miracle in-the-bottle supplements do not work period -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!!!! Rememebr good things take some time to develop and they will if you have patience with your reef tank. basically 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 specifc 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!!

You Now Have a Beautiful Reef Tank 

After 2-4 weeks your rock should be cured and you will then see more corlalline 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 nusiance algae control and to scavange 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 guidlines you should have a great reef tank within a few months.

If you have any questions about curing your rock or any other issue related to your reef tank, please call Dr. Mac toll-free 877-887-5224



Quick Tips

Important things to remember about curing live rock:
1. Live rock is shipped into the US dry and some animals attached to the rock will die off therefore the rock needs curing before adding to your tank.
2. If you do not fully cure live rock this will cause a potentially significant or deadly rise in ammonia.
3. Be sure to check with us about how long we have live rock in stock.  Depending upon when our shipments arrive we might have raw rock of totoally cured rock in stock and this will affect how long you need to cure your live rock.
4. Be less concerned with coralline coverage than rock shape, coralline will naturally grow after your rock is in your tank so shape is most important. 

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