curing live rock

Live Rock doesn’t always look that way but it is and with stuff you don’t necessarily want added to your tank!

First, it is not the actual "rock" that is alive. The rock itself is made from the calcium carbonate skeletons of long dead corals, or other calcareous organisms. It’s the many different micro and macroscopic marine life that live on and inside of it that make it "live". Why do you want live rock? Live rock provides visual landscaping, a refuge for tank inhabitants, and contributes to your aquarium’s filtration system.


On any transported live rock you can expect some degree of natural die-off. Curing is the process of eliminating decaying and dead material from the rock; material that will generate high levels of toxic ammonia and kill off most marine life in your tank. If you haven’t yet acquainted yourself with the Nitrogen Cycle, it is important that you do! You may also see this process referred to as conditioning or cycling. There are two ways to cure your live rock: Using an separate setup or as part of cycling a new aquarium You will find how to details for both below. Follow the guidelines and properly cured live rock will provide an excellent base and biological filter for your successful reef tank’s waste management system.


Sold as Uncured Live Rock: This is collected out in the wild from oceans around the world and has lots of things growing on and in it. Some you want and some you don’t. Shipping live rock involves air freight services and to keep cost down it is not shipped submerged in its native water (cost=$$$$$$$) but shipped dry with some moist newspaper on top to keep it damp (cost=$$$). This and the likelihood that it’s been a few days since your rock was in the ocean means that some of the creatures living in and on it won’t survive. It’s these fatalities that create the need to cure your rock before adding it to an established tank.

Sold as Cured Live Rock: This usually means it has been conditioned or cured and is stable to use in an established tank with minimal concerns. You would purchase cured live rock direct from your local fish store where it has been in their system for some time. It could also be rock you take from another long established tank. It is often used for starting and cycling a new tank setup. Mail order rock is also sold as cured but be careful; you would have to be very confident in their packing and shipping claims. Remember even rock that is sold as fully cured will have some die-off. If you are unsure of its quality or it smells, take the time to cure it in a separate system.


BE PATIENT! – Don’t rush the process. There is no set time frame for curing and it can take from a few days to a few months. The bottom line is if you don’t have patience now, things just won’t turn out well.

Using a Separate Setup to Cure Live Rock


Get your set up ready. Most times you will want a completely separate setup for the curing process. It will need to be heated, well filtered, with a way to circulate and move the water (power heads, submersible pumps, air stones), and a protein skimmer. What you won’t need is a lot of light: say no to algae blooms!

  • The container can be another tank, Rubbermaid™ type garbage can or storage tubs, even a plastic kiddies pool will work. Make sure they are heavy duty enough to handle the weight of the rock you are putting in it. They also need to be large enough to contain your rock, the prepared saltwater to completely cover the rock and allows the equipment to properly operate. The advantage to using a larger volume of saltwater is the more water you have, the more of a buffer you have in controlling the ammonia by product. You can also cycle uncured life rock right in the tank if it is a new tank setup (see Curing as Part of a New Tank Setup below).
  • Saltwater with a specific gravity of 1.021 to 1.025 to completely cover your rock additional supply for water changes prepared to proper temperature, salinity, and aerated. You may also want to prepare an extra large tub of saltwater to serve as a dip and for cleaning. You will see suggestions to use a dip of a higher salinity water, specific gravity of 1.035 to 1.040. Submerge the rock for a minute to remove invertebrates including mantis shrimp, bristle worms, and crabs. They will quickly leave the rock and go into the bucket of water.
  • The heater keeps your water a a constant temperature. You will see a range of temperatures suggested. Some prefer to cure cooler, 72-75°F1saying it is a faster cure overall. Others suggest around 80-82°F to speed up the die off. And you can always stay with the parameters that your current tank maintains. Whatever you choose, this is the temp you will maintain and heat saltwater used for water changes to.
  • The power heads provide strong water flow around and through the rock plus aeration. Proper aeration (and temperature) are needed so that  you maintain high levels of beneficial nitrifying bacteria; their loss reduces the rock’s initial effectiveness as a biological filter.
  • The protein skimmer removes the dislodged matter and nutrients created from decayed and dying matter.
  • You may consider setting up all your electrical equipment on one multi-plug strip plugged into a GFCI outlet. That way you don’t have to remember if you unplugged the heater before a water change.
  • You might consider installing drains in the bottom of a tub to make water changes easier.

You want to closely examine each piece thoroughly and give it a smell. The more nasty the smell, the more likely there is dead or dying organisms in or on it. Look for any obviously dead or decayed material or growth that has a white film or is turning black and remove it. This can be sponges, algae, soft coral or any growth that has a white film or is turning black. Remove them by hand (wearing suitable protective rubber gloves), a small
toothbrush or even a small flathead screwdriver or putty knife. Sponges in particular can be difficult to see and dead sponges are a curing curse so get rid of them now. Use a gloved finger to search for soft spots and remove them. Remove bristle worms still attached to the rock using needle-nosed pliers or tweezers. You may find soft algae or animals like anemones that you want to stay.

Once you are satisfied you have removed all the death and decay you can find, place the rock piece in prepared saltwater tub and swirl and swish it around to remove and dislodge any loose material. You don’t want or need to scrub the entire rock! To do so removes beneficial organisms such as coralline algae and bacteria; on your rock are all kinds of good things you can’t see now, the seeds and spores of everything that lives out in the ocean, that then may grow out down the road! You can then put the cleaned rocks in your ready to go curing setup.


Your primary concerns now are ammonia removal and circulation.

  • Make sure have really good water flow around and through the rock; occasionally use a powerhead or turkey baster to blow out around all the exposed rock surfaces. You will need to add purified water to the curing setup to keep up with evaporation and will test daily to make sure you are keeping a constant salinity level of about specific gravity 1.025.
  • Water changes will help you keep the ammonia level from getting too high. There are varying opinions on how often. Five to ten gallons every other day is not unheard of with more if the water stinks or is turning yellow. Other suggest a water change schedule of 25% to 50% weekly. If you are not skimming you will definitely be changing more water, more often.
  • Closely monitor your protein skimmer, especially in the first few days as the nutrient and material load will cause excessive foaming and require cleaning. You may want to hook up a drain hose to the cup. Make sure you have plenty of reserve for the waste material the skimmer will be removing. The curing set up may have a strong smell for the first 3-4 days but should dissipate if your protein skimmer is working and being maintained for optimal performance and you are doing water changes.
  • Your rock needs minimal to moderate light. In the beginning too much light will only cause much nuisance algae growth in the nutrient rich environment. Too much light also causes coralline algae to fade and die – they do not like intense light. You can cure without light but if you are going to light your curing tub or tank, start with just fluorescent light, preferably only blue actinic light on for 2-4 hours daily during the first two weeks of curing. You want some light for the coralline algae to survive but not too much.

In about a week things will start to calm down. You can start testing for ammonia from the start but realistically, you know you have it and way too much so the point is a bit moot. After the first week, start testing every two or three days. The ammonia and nitrite leves should continually drop. Also inspect your rock regularly for unwanted life forms. A flashlight at night is a good way to see what you don’t during the day. You can use a nylon brush or old toothbrush to remove dead material or white film on the rock between water changes also.


Expect the process to take about 2 to 4 weeks. When the ammonia and nitrite levels drop to 0 you are done! There should be more good ammonia eating bacteria than bad ammonia making ones. Your nose is a good double check. Give some individual pieces a good sniff. If the pieces still stink, then things are still decaying; fully cured rock has a clean "oceany" smell. If all smells good, you can now move the rock from the tubs into your established tank.

If you can stand waiting, let your cured rock hang out for a couple of weeks more as added insurance. You will also want to acclimate your newly cured rock to the lighting you will need for corals and other inhabitants to survive. Start slowly with lighting the first week. A couple of hours of blue light followed by a couple of hours of white-daylight. Increase to four hours a day of white-daylight between the sunup and sundown blue period. Then slowly build up to 8 hours of daylight bracketed with a couple of hours of blue light dawn and dusk. when you start the white daylight intense lighting  get grazers (see What’s a Clean Up Crew) on it right away.

Curing as Part of a New Tank Setup

This method is only for new aquariums that do not contain any marine animals, coral, fish, etc. You are in essence following the steps above with the container being the actual aquarium your final setup will be in and curing the live rock as part of cycling – that is getting theNitrogen Cycle established in the new tank by establishing bacterial
colonies in the live rock that convert ammonia (NH3) –> nitrite (NO2) –> nitrate (NO3)

The needed species of nitrifying bacteria are present everywhere. Once you have an ammonia source it’s just a matter of time before you have bacteria colonies establishing colonies. The initial ammonia source can come from your live rock. It also can be introduced by adding one or two live fish, a piece of raw shrimp, or commercial preparations of nitrifying bacteria colonies. The cycling process starts with ammonia levels going up and then suddenly plummeting when the nitrite producing bacteria take hold. Nitrite levels will then continue to increase as nitrite producing bacteria take hold. Then when nitrate forming bacteria take hold, nitrite levels fall as it is converted to nitrate. When ammonia and nitrite levels are 0 and nitrate levels rise your tank is deemed fully cycled.

  • Set up the new tank installing all filtration, circulation, heater, chiller, and accessories. (see Reeftank 101) Mix and fill the aquarium with fresh saltwater with a specific gravity of 1.023-1.025. Check for leaks, turn on all the filtration equipment, set heater and / or chiller to maintain your desired temperature, usually a range between 75-80°F.
  • Follow the steps above in ‘When Your Rock Arrives’ to remove loose organic matter, debris, sand and obvious dead matter. Arrange the live rock in the tank, making sure to create a stable and suitable foundation for your future inhabitants.
  • Have saltwater mixed and ready to perform water changes.
  • Siphon out organic matter and loose debris that accumulates on the tank floor.
  • Your filtration system will get a workout so keep up with its maintenance and cleaning during this process!
  • Keep the lighting system off during the cycling process to reduce the chance of  unwanted algae growth.
  • Keep a journal of your water parameters during the cycling process. It will help you note subtle changes and track the process. Besides testing for ammonia, nitrite and nitrate consider tracking dKH / pH as carbonates are used up in the cycling process creating pH drops and slow nitrifying bacteria growth.
  • Test ammonia and nitrite level weekly. When they measure 0, do a 20 – 50% water change. Then after 24 hours, check pH and adjust to obtain the desired level of 8.0-8.4.
  • With the nitrogen cycle established, you are ready to move forward and begin adding inhabitants.

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