Live rock.
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This photo is a royalty-free image courtesy of Adrianna Calvo from Pexels

This is an article for beginners. Since I didn’t see a sticky or article on this topic, I decided to tackle it myself. There are lots of differing opinions on how to cure live rock, and I’m going to explore here as many as I can find. I will include in the body of the article some common questions.

Where appropriate, I have included some comments from forum members noted in red.

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This article is on curing live rock. This article is not on curing dead rock, dead live rock, base rock, Marco rock, home-made rock or any other rock. I’m referring to rock that came out of the ocean or some on-land farming facility that creates live rock or from someone else’s tank.

I’m talking about rock that’s wet and was just shipped to you or you just got it out of a tank at an LFS (local pet store that sells fish and fish supplies) or someone else’s aquarium. I’m talking about rock that has all kinds of live organisms on it, large and small, and perhaps a few dead or dying ones.

Safety with handling live rock

Before I go into detail below, I want to address some safety concerns, in case some readers don’t make it all the way to the end. If you have ever washed anything with a scrub brush, then you know that there’s plenty of back-spray.

Reef2Reef recommend that you be very careful when cleaning or handling live rock. Some people develop sensitivities to the rock and/or to the saltwater and other microorganisms. Please wear gloves. Please wear safety glasses. Consider wearing a mask or face shield. Never boil live rock and get your face in the steam.

While some readers will think this is overkill, personally, I have a lot of allergies, and I think it’s better to be safe than sorry. There could be microscopic bits of things like zoanthids or anemones that you do not want on your skin or in your eyes.

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Why do reef aquarists use live rock?

Reef aquarists use live rock because it is colonized with bacteria that aid in filtration. This bacteria converts ammonia from waste to nitrite, then nitrite to nitrate, then nitrate to nitrogen gas.

The benefit of using live rock is that the rock is already colonized with this bacteria more or less, depending on the condition and previous environment of the rock. Live rock is or should be very porous. This means that there is an enormous amount of surface area on and inside the rock for the bacteria to cover. More bacteria means more filtration.

What is live rock made of?

In theory, it can be made of any kind of rock that has been sitting in the ocean or an on-land tank for the purpose of being colonized with micro- and macro-organisms. Traditionally, it's made of calcium carbonate or old coral skeletons, and is very porous.

Christmas tree worms (Spirobranchus giganteus) embedded in coral.
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This photo is a royalty-free image from Pixabay.

How much live rock do I need?

That’s hard to answer because some rock is more (or less) porous and weighs (more or) less than other rock. There’s a general and vague rule of thumb to use 1.5-2.0 pounds per gallon of tank water.

Do I have to use live rock?

No. You don’t. Live rock is not cheap, and many people use other kinds of rock and only a little live rock to “seed” the rest of the rock. The downside to not using a lot or any live rock is that it takes much longer for beneficial bacteria to colonize your rock.

The benefit of using live rock is the significant biodiversity you add to your aquarium by using it. The downside is the risk of unpleasant hitchhikers (see below).

Can I seed my live rock with live sand?

Maybe. The microorganisms living in sand are not necessarily the same ones living in live rock. So, yes, eventually, some bacteria will colonize your rock, but it will take time.

What is curing live rock?

Curing the rock means that you clean off any dead or dying organisms and allow the rock to stabilize in an environment (like a Brute trash can) away from your display tank if you already have fish or other critters in there.

What’s the difference between cured, uncured, or partially cured rock?

The differences are in how the rock was treated and/or handled after it was taken out of the water initially. If the rock is already partially cured, you should have less die-off once the rocks gets to you, but you may also have less biodiversity.

Can I cure the live rock in my display tank?

Yes, if you are just starting up the tank. No, if you already have livestock in your tank.

The advantages of curing the rock inside the display tank are as follows: 1) it’s easy to watch what’s happening or not happening to your rock and your water column, 2) you don’t have to move the rock into your display tank after it is finished curing (if you cure it somewhere other than in the display tank.)

The disadvantages of curing the rock inside the display tank are these: 1) once the rock is inside your display tank, it’s not so simple to remove any unwanted hitchhikers and 2) curing live rock can stink with a crash for weeks on end—you may not want that smell in your front room.

A nice reef tank with plenty of live rock.
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This photo is from the Reef2Reef archives courtesy of @kennydoll, ©2019, All Rights Reserved.

What’s a hitchhiker?

A hitchhiker is an organism that comes with your live rock that you did not intend to have. Some hitchhikers are good: like a zoanthid or a porcelain crab. Some are not so good: like a pest anemone or a mantis shrimp.

How can I separate out my hitchhikers to know if I want them or not?

There are a few things you can try, but there are no guarantees that you will find them all or identify them all in the beginning. Microscopic pieces of coral or algae will not be obvious right away.

Some people recommend that before you cure your rock, you place it in a bin or bucket with water that is saltier than usual, like with a density of 1.04 g/cm3 for one minute, then back to normal saltwater.

Some recommend leaving it a bit longer than that. Some recommend putting your live rock into fresh (RO/DI) water for a minute or two, then back into saltwater. The problem is that if you leave the rock in the fresh water too long, you risk killing a lot of the beneficial microorganisms that you want.

Some recommend spraying the live rock with a stiff spray of saltwater. Some recommend spraying the live rock with club soda, then put it back into saltwater.

Generally, it’s recommended to have some tweezers or needle-nose pliers handy to pull things off the rock. Also, some recommend putting down egg crate at the bottom of your curing container so the rock stays off the bottom surface, but so there’s room below it for other critters who jump ship.

Some aquarists also treat the rock with Flatworm eXit (Salifer) as part of the curing process. I have no opinion on this. It’s your tank, and as I frequently say, there are no aquarium police to monitor what you do or how you do it.

Keep in mind that the more actions you take to rid yourself of hitchhikers, the more likely you are to damage the good things on your rock that you want in your tank.

Comment from @AlexG: hitchhikers that I value from my live rock and sand in my system:
  • Mysid Shrimp
  • Limpet snails
  • Ostracods
  • copepods
  • amphipods
  • isopods
  • worms
  • unidentified pods
  • brittle stars
  • macroalgaes
Comment from @ca1ore: Most of my live rock came fresh out of Florida in the late 1980's. Loads of cool stuff - worms, a few mantis shrimp and even a common octopus.

How do I identify the hitchhikers on my live rock?

If you google it, there are lots of guides to live-rock hitchhikers. You can also post photos on our forum and forum members will try to help you.

So, how do I cure the live rock?

Okay, here’s the fun part.

Take your rock and look at it. Rinse with saltwater. If you see a lot of dead or dying stuff on it, then use a stiff plastic brush or toothbrush or screwdriver and clean it off. Rinse. Set aside.

Prepare your display tank or a separate container with seawater of the appropriate density (like 1.025 g/cm3), appropriate temperature (like 78F), and some water movement (like with a powerhead or airstone or both or several).

Now put your rock in your container. Make frequent large water changes like 2-3X per week. And just keep the rock in there with the equipment running. If you see a bunch of die-off, you can pull out your rock, brush it, rinse it, and put it back into the container. When changing water, be sure to siphon out detritus from the bottom of the container.

Keep any live rock rubble that falls away. That’s useful for putting in a refugium among other things. You can always keep the rubble together in a small plastic container that has holes in it—like a plastic container that strawberries come in. Live rock rubble could also be used to seed dead rock.

Comment from @Gregg @ ADP: For new tanks, this is what I do. Light rinse of rock to get some of the mud off, and in it goes. I’m good with whatever comes in...I’ll deal with it eventually.

Comment from @garbled: If you bucket-cycle rock to completion, and then add to the tank, I generally find that the algae blooms are smaller, and less gruesome, and probably a bit shorter, but the rock is less awesome.

People find some truly amazing hitchhikers on live rock when you use the "chuck it all in" method. I've seen posts with corals, sponges, tunicates, and even *fish*. Also crabs, and shrimp, which maybe you don't want?

Then: It's helpful to do water changes here [if you chuck it all in], as it helps preserve the life on the rock. I'd recommend an ammonia-alert badge, and a few nitrate tests as you go. Ideally the skimmer and chaeto would take care of it all, but you should keep some water in your back pocket just in case it gets away from you a little bit. (like something big dies in some crevice.)

Why do I need water flow when curing live rock?

You need water flow for the same reasons you need flow in a mature aquarium set-up: water flow agitates the surface of the water to increase oxygen exchange and oxygenate your water. The flow also brings nutrients to organisms that need them and takes waste away from organisms that need to get rid of them.

Do I need a skimmer?

Maybe. That’s impossible to answer because it depends on how much rock you have and how much die-off you have. If you have a small amount of rock and are doing lots of water changes, you can probably do without the skimmer. If you have a lot of rock, a lot of die-off, and don’t relish changing water as much, then definitely add a skimmer to the mix.

Should I use lights while I’m curing the rock?

Maybe. It depends on who you ask. Most people these days tend not to light live rock when it’s being cured. The thinking is that giving it a lot of light encourages the growth of undesirable algae. This group advises just to give the live rock ambient light from the room.

Another set of beliefs, subscribed to by the famous aquarist, author, and breeder, Bob Fenner, is to fully light the live rock on a timer just like you would the aquarium. This philosophy is that the risk of an algae bloom is not as important as saving as much of the life on the rock as you can. Much of this life is dependent on light to survive, so you give your rock more chance to flourish by lighting it.

Does all the live rock I buy have to be cured?

Probably not. If your LFS has had the rock for a long time and has taken some care to remove the dead matter, do plenty of water changes, keep it at the right temperature, and have plenty of water movement in the tank, then the rock may not need much or any curing.

However, it’s a good idea to check it out carefully at home and maybe keep the rock by itself for a bit to inspect it for hitchhikers and do some water testing before putting it into your tank permanently. Beginners are often in a hurry to do things, and in reefkeeping if you act in haste, you can repent at leisure.

How do I know when my live rock is finished curing?

One indicator of the need for curing or further curing is the “sniff” test. Does it smell like an ocean breeze or your dog’s breath on a bad day? If it smells off, then it’s not done curing.

The other indicator is through testing. Most people will test the water that the live rock is curing in. If you have been testing steadily, then you will see ammonia increase, peak, then drop off. Then nitrite will increase, peak, then drop off. Then nitrate will increase, peak, then drop off. In theory anyway. When all those indicators have come down, and the rock smells good, it’s done.

How long does it take to cure live rock?

It depends on the rock and how much die-off it has and whether it was already cured at all. It can take as little as a week or as much as a month or more. See sniff test above.

What happens if I don’t cure the live rock or don’t cure it fully?

You risk creating a cycle inside your aquarium, which is not healthy for your livestock. This will require more water changes and constant testing or you can kill what’s already in your tank.

Does live rock from different parts of the world have different micro- and macroscopic life on it?

Yes, probably, and the rock may look different, too. Some rocks will be denser than others, some will be more branched, and the hitchhikers may vary. What’s most important is that you want your rock to be porous. The more porous it is, the more surface area is available for bacteria to colonize.

When I start with live rock, is it a fix-it-forget-it thing for the life of my aquarium?

It depends on who you ask. Some reefers have a very happy stable tank for many years. Many experts, however, recommend you take out a little and add a little of fresh live rock after each year. To “top up,” so to speak, the beneficial bacteria. You may want to keep this mind while aquascaping—that you might want to take a little rock out and add some new rock at a later date.

For further information about rock for the aquarium, please read these two articles: Reef Aquarium Rock, Part 1, and Part 2.

References:

http://reefkeeping.com/issues/2004-05/rs/feature/index.php

https://www.advancedaquarist.com/2003/2/beginner

http://www.wetwebmedia.com/Curing Live Rock.htm

https://m.liveaquaria.com/article/209/?aid=209

http://www.saltwateraquariumblog.com/cure-live-rock/

https://en.wikipedia.org/wiki/Live_rock

https://arcreef.com/live-rock-hitchhikers/

https://www.lionfishlair.com/hitchhikers-guide/

http://www.wetwebmedia.com/invertidfaqs.htm



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Author Profile: Cynthia White

Cynthia received her BA in English from NYU. She has been a freelance writer and editor for over 20 years. Now she is a writer and editor on staff at R2R, where her forum nickname is Seawitch. She admits to knowing how to shoot a gun.

For 15 years, she kept a dozen freshwater tanks, bred cichlids--Cyphotilapia frontosa--and sold them to pet stores in Calgary. Finally, after years of study, she has come to saltwater side. She lives in British Columbia, Canada, with her husband and three special-needs dogs, a five-minute walk from the Georgia Strait, the Pacific Ocean between Vancouver Island and mainland British Columbia, where the water temperature ranges from about eight degrees C (46F) in the winter to 15 degrees C (60F) in the summer. Bring your dry suit. And some hot coffee.