What is Live Rock, Anyway?

[leebca]

One of the important features of the aquarium for fish is how their nitrogen wastes are handled. In an aquarium full of corals, very little nitrogen waste is produced and the aquarist can almost ignore these kinds of wastes. But a marine aquarium stocked with fish, snails, crabs, shrimp, etc., has a large source of nitrogen wastes that need to be processed quickly in order to prevent harm to the fish and marine life.

The aquarist depends upon the microbes in the aquarium to enjoy the ability to maintain marine fishes. In essence, I like to think that the real hobby is how to keep and maintain microbial life!

The biological filter is the scene of the 'action' when it comes to processing nitrogen wastes (nitrification = converting ammonia to nitrite and nitrite to nitrate), but the bacteria that process wastes are everywhere in (and around) the aquarium. This should be made clear. These bacteria are everywhere. They are found in the air, in soil, in water, on human skin, etc. In the marine aquarium, they attach to any surface that will have them (the aquarium wall, substrate particles, equipment surface, pipes, filter media (floss, cloth, carbon, resins, etc.), decorations and of course, live; dead; or base rock). BUT (and this is important) the real value of real live rock is not as a surface area for these kinds of nitrifying bacteria, but as a home to another set of bacteria. Keep reading.

Live rock has some special characteristics that make it of particular value with regards to its role in handling nitrogen wastes. The aquarist that wants to keep fish and/or a reef aquarium with fish, needs to understand more about this value. First though, let's get on the same page for our names and definitions. There are different levels of life on the rock we use in the marine aquarium.

Rock doesn't live. So how can it be alive? It's the organisms on and IN the live rock that gives it that name. There are different levels of life on/in rock that qualify the value of the live rock.


A ROSE BY ANY NAME. . .

There is no national or international standard when it comes to naming marine aquarium rock. Even if you don't buy into my naming system (see below) keep in mind that when you communicate with someone regarding aquarium rock that the both of you are using words that you first define to each other. There are many people in the hobby that would mis-represent rock by carelessly tossing about words. Don't be fooled. Ask.

Rock with no life in or on it is called 'dead rock.' Some people call this 'base rock' but I don't. You'll find that the use of the phrase 'base rock' means different things to different people. Here I want to be clear and, whatever you choose to call it, make sure you and the person(s) you are communicating with are using the same definitions not words.

Rock with some coralline life on it, but nothing much else is called 'base rock' or maybe you're more comfortable calling it 'live dead rock?' It is more than dead rock, but isn't fully functional like live rock, as it relates to the handling of nitrogen wastes.

'Up' from the level of base rock, rock can have other organisms living on it (e.g., polyps, complex algae, pods, corals, etc.); or organisms living on and IN it. This is called 'live rock.' But there are different levels of life on and in live rock, which make live rock have different 'levels' of being alive.


HOW ALIVE IS LIVE?

Rock right out of the ocean/sea is true live rock and stands as the 'most alive' of the live rock. It has this distinction by virtue of the diversity of life on and in the rock. It has a grand diversity of life and lifeforms. It took decades to hundreds of years for that life to take up residence on and in that rock. But this rock can't be shipped to the user, without being submerged in water. Decades ago we used to get this kind of live rock from the sea. It was shipped in water and had ALL the lifeforms represented on and in it as if it was still in the ocean. Today, shipping rates and fuel costs prohibit this. So the rock ships without water. Often it is kept moist by wrapping it in paper/newspaper wet with saltwater.

To ship moist like this without 'rotting' along the way, the rock first has to be cleaned of organisms that would die when they are exposed to air (e.g., sponges). During this process, most (if not all) crabs, shrimp, etc. are also cleaned off.

Many but not all things in and on the rock die during moist transport. So the wholesaler/LFS or aquarist gets the harvested rock and has to further cure it. After curing, this is about as alive the live rock will ever be for the aquarist. It's a considerable difference from the rock that was in the sea as far as diversity of lifeforms is concerned. But this is what we call and mean by 'live rock.'

But, even more cleaning and curing can be done along the way which further reduces the diversity of life on and in the rock so that the aquarist gets various levels of life on and in the live rock. Although curing makes the rock less polluting for the aquarium, it may also destroy and may remove more of the natural lifeforms in and on the rock.

Ever read or hear of fully cured live rock? Seems like an oxymoron. If the rock is fully cured, then it should be dead rock, right? A misnomer for sure, but we accept it. In general, this term means the live rock is ready to be put into the aquarium, but the aquarist should ask just how cured it is. Is there any lifeforms still in and on the live rock? If so, find out what they are. If you're told it is 'live rock' because it has coralline growing on it, don't buy it. Offer to buy it as base rock until other life forms on and in the rock are known to be present.

Just because the rock is covered with coralline, it doesn't mean it is live rock. That is why I've built in the category/name of dead rock and base rock to account for this fact.

There is also 'aquacultured live rock.' This is dead, base, or man-made rock that is placed in the ocean. It will develop lifeforms on and in it, but because it hasn't been in the ocean for decades, the diversity of life on and inside this rock is limited. This doesn't mean this rock is 'bad.' It is very responsible for aquarists to try and seek out buying cultured live rock, in order to spare our natural reefs. But just don't expect the entire width and breadth of lifeforms in such rock as you would from live rock having been in the sea for decades. This rock is also usually shipped moist (wrapped in paper), so some initial or at least final curing is needed.


THE VALUE OF LIVE ROCK

Remember the nitrifying bacteria I mentioned early on that handle nitrogen wastes in the nitrification process (converting ammonia to nitrite and nitrite to nitrate)? These bacteria are on live rock. They are on dead rock and base rock too. The rock just serves as a surface for them to stick to. Fish wastes and oxygen in the water provide their nutrients/food. So no matter what rock is put into the marine aquarium, it will act as this nitrification part of the biological filtration system (after enough of these bacteria multiply). This is not the real value of live rock, however, when it comes to bacteria.

There is another set of bacteria that is responsible for turning nitrates into nitrogen gas (and other compounds). The process is 'denitrification' and is performed by denitrifying bacteria that don't like to live in areas where there is oxygen. They are found in tight-packed soils, in lower levels of substrates, inside of porous rocks and places (like tiny crevices and worm holes (with or without the living worm still there!) where there is low oxygen content.

The real value of live rock in the marine aquarium is what these denitrifying bacteria are doing just under the surface and in crevices of the rock. Denitrifying bacteria (unlike the nitrifying bacteria) can only live and grow where there is little or no oxygen, so we don't find them growing everywhere. (NOTE: They can be found almost everywhere, but just not growing.) The real value of live rock in the biological filtration process is the denitrification it can perform in the marine aquarium.

How live rock performs the denitrification isn't fully understood. Many theories and models have been proposed. That topic is a whole other post in of itself! Scientists try to explain what we know: Live rock not only will function in the nitrification process but will also function in the denitrification process. So the 'right kind' of live rock can help remove nitrates in an aquarium. (See: Denitrification v. Nitrification for more non-technical info on these chemical processes).


GREAT EXPECTATIONS

If the aquarist expects live rock to do the full function of nitrification and denitrification then the rock must be alive in the sense that there are still living organisms (e.g., worms, etc.) inside of the rock AND that the rock will perform denitrification. Such live rock has not been stripped of life. nor cured to kill what's inside (e.g., by freezing, boiling, baking, or chemically treated), nor transported dry (but wrapped in at least moist paper).

Probably the biggest error for new aquarists is the thought that if dead, home made, or base rock is placed next to live rock in the marine aquarium, that these will turn into live rock. NOT.

No matter how long dead, home made, or base rock sits next to live rock in our aquarium, the lifeforms that live inside of live rock will not move over to the dead or base rock. Those rocks will never become live rocks! Why? Because the organisms inside the true live rock don't reproduce in our aquariums These worms and other special lifeforms responsible for the rock performing denitrification, will not spread. They cannot move to other rock and they cannot reproduce/multiply in the aquarium. In fact, this is one reason why some aquarists claim that live rock should be replaced every 5 to 10 years. The lifeforms inside the rock will die off of their own accord, and the help the live rock gave at removing nitrates will diminish as the rock ages. Some claim that once coralline algae covers over the crevices and these worm holes, that the rock will loose its ability to handle nitrates, too. Makes sense. So maybe don't be in such a rush to cultivate a lot of coralline if you need the denitrification!

What will happen when dead, home made, and base rock is put next to live rock is the organisms that can spread will do so, to the other rock. Such organisms are coralline algae, other algae, pods, polyps, etc. But the worms and specialized lifeforms don't spread! So the aquarist can use base rock, home made, or dead rock mixed with live rock and still have (eventually) a nicely coralline-coated aquascape, but the dead and base rock will not help much in removing nitrates.

When the place that you are thinking about obtaining live rock from tells you they made their own live rock, or that they put base rock next to live rock in their tanks, then you should be well armed with the truth -- they did not make live rock. They made base rock. It is only covered with coralline and a few other organisms and lacking the 'inside' organisms.


HOW MUCH IS NEEDED?

The hobby likes to measure live rock in pounds. But the weight needed really depends upon the density of the rock and how much the rock is alive. The live rock right from the ocean is most efficient, but as previously written, no longer available to the landlocked hobbyist. So to compensate for the loss of diversity and organisms, more live rock is needed to perform denitrification.

Most general rock of 'average density' (whatever that means) needs to be in a marine aquarium supporting fishes at a rate of about 2 pounds per gallon of display tank volume. This weight of rock can be spread out in the display, sump, and refugium to provide more swimming space in the display tank, but at least 75% of it needs to be in the display at the immediate source of where the majority of nitrogen wastes are produced. The is the quantity of live rock needed for a fish only with live rock (FOWLR) aquarium. Although marine fish are not sensitive to nitrates, the use of live rock can reduce the frequency of water changes and produce a much healthier environment for these lifeforms. 30+ years ago, live rock wasn't used in fish only aquariums and the fish did just a well in the hands of advanced aquarists. A reef aquarium can get along with less weight, provided this aquarium is understocked with nitrogen waste producing lifeforms (fish, snails, shrimp, crabs, etc.). An aquarium without fish, crabs, snails, and other nitrogen waste producers can maintain low nitrates with very little (or no?) live rock.

When should it be replaced? When the aquarist starts getting elevated nitrate readings (usually after 8 years) with the usual water changes and maintenance and bio-load. How do you replace live rock? That's another story, not easy nor straightforward, and another post!


A JOB WELL DONE

In order for the rock to do the best job it can as far as nitrification and denitrification is for the nitrogen waste products to get to the rock. This is where the aquarium system plays a role. Specifically, it is about circulation. The fundamental minimum circulation for live rock is 8 to 10 system volume turnovers per hour. Above this figure, circulation may be needed (e.g., in reef tanks) for certain sessile invertebrates, corals, etc. that depend upon greater circulation to carry off their wastes and/or to bring nutrients to them. So for a FOWLR aquarium, without special marine life needing additional circulation, the target is 8 to 10 system volume turnovers per hour. The "8 to 10" is 'calculated' by adding up all the gallons/hour flow rates of: powerheads, internal pumps, and external pumps (used for systems with sumps and/or refugium).

Now that the right turnover is achieved, the flow must be evenly distributed over and around the live rock. No dead places. All exposed surfaces of the live need to have some flow around them. Adjust and direct the various flows to achieve this goal.


ALTERNATIVES

There are other means to perform denitrification. A deep sand bed is used for this purpose. Special filters are made to house denitrifying bacteria in low oxygen areas. Special media exists to also provide a place for these bacteria to grow. But nothing is as efficient as live rock, even after it's been cured so much by the time it got into the aquarium.

Then there are also chemical means to remove nitrates (absorbing and reacting compounds).

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I hope this post has clarified and enlightened the reader on live rock. All rock has its place. Just be sure you know what you're buying, buy what you want it to do, and buy enough!

[underseaworld]

I did not know that base rock would not become live rock. I was told by lfs that the man made rocks or base rock if placed next to live rock would become seeded and become live rock. Well that puts and end to me making any more rocks. Why waste my time if it does not perform like live rock. Well it is the weekend and off I go to get some live rock.

[leebca]

The problem with the 'live rock' issue is that there is so much mis-information floating around. About the least informed are the LFSs (IMHO). As live rock becomes more and more expensive and scarce, LFSs are taking 'short cuts' by purchasing base rock and, like you wrote, putting it in tanks with live rock. Then at some point in time, the LFS sells that base rock as 'live rock' at a considerably higher price. These LFSs should be avoided, in my opinion. They are deceptive or ignorant, neither case says much for them.

When dead rock or base rock is placed in an aquarium about the best you can hope for early on is that the rock will be coated with bacteria that perform the nitrification process. Later, it will also become encrusted with coralline and algae, and serve as protection and safe harbors for copepods.

The 'man-made rock' you were making is what can be used as starter material for aquacultured live rock. Placed in the ocean or sea, it slowly becomes active (able to perform denitrification) in a few years and really becomes valuable live rock in a few decades.

We can't beat Mother Nature; we can only compete with Her. It's just another reminder that the home aquarium isn't a piece of the ocean.

That doesn't mean the homemade rock doesn't have its value and purpose. It will still serve as a home to nitrifying microbes, turn colors with coralline and algae growth, and look just the way you want it to look.

[Ixthys]

Hi Lee.

Good write-up. I do have a question!

If I take a piece of live rock from the ocean, leave it out of the tank for a year, and then put it in a tank that has live rock in it, if I understand you correctly, you're saying that at most this rock will become "base" rock and never achieve "live" rock status again (by your definitions above).

I'm assuming you're saying this b/c the organisms inside the rock are "trapped" and are now dead. No new organisms can get into the rock to replace them.

I find this hard to believe. I also am curious how it was scientifically proven. Have you seen a study on this?

I personally subscribe to the notion that the live rock is extremely porous and covered with essential bacteria, both inside and out. Diffusion of nitrite/nitrate through a solid (non-porous) media can't occur at a rate acceptable to the health of our tanks. At least that would be my hypothesis if if ever did research again!

[charlesr1958]

"you're saying that at most this rock will become "base" rock and never achieve "live" rock status again (by your definitions above)."

A base rock will never achieve the status of live rock simply because it will never achieve the diversity of life found within truly live rock. Our systems are very unlikely to ever be able to provide the diversity of life that can colonize a rock nor able to allow what life there is in other rocks to reproduce successfully and colonize a base rock. The most you can hope for a base rock to achieve is a coating of algae, maybe some transient sponges and the odd worm or two that happened to crawl over from other rocks. If you get a smattering of other life forms on it, consider yourself lucky. Here is my take on Live Rock / Sand.

Chuck

[leebca]

[Although in the following text I use the word anaerobic the reader should keep in mind that these 'areas' are not necessarily void of oxygen. They may be suboxic or low in oxygen, but not truly anoxic.]

Ixthys,

I personally subscribe to the notion that the live rock is extremely porous and covered with essential bacteria, both inside and out.

Definitely. But your 'subscription' doesn't extend far enough.

One model is the 'worm theory.' Worms inside the rock, through their movement and activity and their pumping action, bring water baring nitrates into the rock where, in an anaerobic environment, microbes work on the nitrates to produce nitrogen, ammonia and organics.

Another model: The denitrification is done by bacteria or archaeans, or both, and so as long as the live rock remains porous and there's enough animals to support reasonable flow, the situation might remain stable for a reasonable period. Coralline (I use this term to mean all algae) growth will block off these 'holes' (pores) and crevices and the water flow to the anaerobic areas is cut off and thus the rock becomes less useful with time. If this model holds up then as base rock 'ages' in a reef tank where carbonates, alkalinity and calcium is maintained, the coralline will close off the holes at about the same rate as the bacteria can do their job. So, the base rock remains base rock in the long term.

Another model: One recent study (Könneke et al, 2006) has shown that the archaeans are also capable of nitrification. In this model the nitrification organisms and denitrification organisms are working together in the anaerobic areas of the rock. The aerobic nitrification can occur in this area, but at a retarded rate; the anaerobic denitrification can occur in this area, but at a retarded rate. A variation on this one includes the presence of microaerophiles. Unless there is aided water flow into these areas, the rate of metabolism is slow.

Another model is that these anaerobic areas contain faculative anaerobes that in essence metabolize the wastes similar as in the above model. Here the proposed model is that the aerobic organisms create an anaerobic environment for the anaerobes to denitrify. In yet another (similar or a variation) model, the living worms create such an anaerobic environment through their respiration.

There are other models. Some are extremely complex. But no one seems sure which is the right model or if it may be a combination of the models. Microbiologists' understanding of the archaeans is slim. And when it comes to aquariums, there is little interest in furthering the understanding of this mechanism.

One underlying commonality each of the above models have is dependency upon water flow into the anaerobic areas. It is known that diffusion isn't fast enough to keep up with the denitrification of the water that live rock has shown. Your hypothesis is correct. Diffusion models don't produce enough denitrification as what live rock produces.

A particularly good reference which contains further references was written by Dr. Shimek: http://www.reefkeeping.com/issues/20...ture/index.php

Seachem gave a presentation at MACNA regarding the above. Seachem is doing research on live rock and its affects on ammonia, nitrite and nitrates in reef tanks. You may wish to contact them for more information on their progress.

You should try your own controlled experiments. We need more information. As has been shown, the denitrification performed by base rock is depressed to near zero; the denitrification performed by live rock diminishes over time; the denitrification of base and dead rock put into an aquarium with live rock, when taken out and tested should show that it has a diminished denitrification ability, if at all.

Dr. Shimek is much more knowledgeable about the diversity found on true live rock vs. base/dead rock placed next to true live rock. He's written in threads:

The answer to that one is that it can never acquire the biological diversity found in natural live rock. That diversity comes from the colonization of animals and other organisms, and the "pool" of colonizing organisms would be limited to those in the tank in the first place and this is a pool that is minuscule compared to what is on a real reef. So.. the [base] rock may become colonized, and even have a lot of animals in/on it. However, the organism array on it will never become particularly diverse.

I'm assuming you're saying this b/c the organisms inside the rock are "trapped" and are now dead. No new organisms can get into the rock to replace them.

I'm not assuming that because of. . .

Dr. Shimek again:

The live rock may be collected and shipped "as is," or it may be "treated" or "cured" in different ways to remove various components of, primarily, the animal fauna living on and in the rock. Some collectors and vendors go to great lengths to ensure that their rock is free of as much of the material as possible that can potentially rot and foul a system. These vendors provide rock that often is covered with a large amount of coralline algae, and very little else. This rock is free of much of the material that can die in transit and rot in the destination tank. It is also free of most animal life. This rock can provide a beautiful backdrop or substrate in a tank, but, unfortunately, it simply can't provide much in the way of biological filtration. The small animals that moved water through the rock are not only dead and gone, but there is likely no fauna available to colonize the live rock and replace them in the destination tank. This rock is full of dead space and algae. Once in the destination tank, such rock will become populated with algae, much as it was in nature. However, there will be no water pumped through the small channels and pores in the rock, and such pores will begin to fill in, primarily by the growth of algae. Such rock has quite a potential for the internal buildup of noxious compounds. If a significant amount of algal and worm biomass was killed by the collection and curing process, this material will mostly remain in the rock, where it will rot. Instead of functioning as a biological filter, such rock would contribute to the system's organic load as these rotting materials slowly diffuse out of the rock over a period of several months.

If you put your dried live rock into the above statement, your rock Ixthys will have killed off the higher organisms responsible for water flow. Their (not really trapped) organics is now a source of pollution to the tank. It isn't because no other organism can get in there, it's just that the right kinds of higher life forms can't take over those that died.

HOWEVER, I believe such rock has allowed the living anaerobic microbes to form spores before they dried out. When that rock is wet again, the anaerobic bacteria able to function again in the suboxic environment will once again function. But the other part of the need is how will water move into that area? It still begs the question of what is happening other than diffusion. If you subscribe to the worm model, then the dried rock will have killed the worms that dried out. These worms aren't there to pump water/they have no long-term ability to survive drought. So such dried-live-rock returned to the wet aquarium environment will have some denitrification ability. But no more than normal diffusion will allow which isn't enough to sustain a reef aquarium with a medium bio-load.

It would be an interesting experiment. Take the same large piece of live rock. Split it. One piece goes into an environment where its denitrification processing ability is measured. The other is allowed to dry out for a year. The dried one, placed back into the above same environment where its denitrification ability is measured. One thing would be certain, the dried live rock will contain less diversity than the original piece.

I would suspect that such dried live rock would fall in between the scheme of 'live rock' and 'base rock' in my definitions.

[leebca]

Chuck,

That reference of yours is a fair summary of what I wrote. I would disagree in the sense that base rock does contain some life on it. Quite often base rock contains coralline, algae, and microbial lifeforms.

Thanks for sharing.

[Ixthys]

LIVE rock that has "died" by being left out of a tank can be put back in a tank with LIVE rock that has not died, and serve an equivalent value as the other rock in that tank currently, once it has cured. No doubt it will have a period of cycling from the dead organics that are left inside, but eventually it will be colonized by the bacteria in the adjoining rocks. And, as you correctly pointed out, by the spores that have gone dormant.

I definitely agree that the more death that occurs on LIVE rock (between the time it is harvested from the ocean and the time it hits your tank water) the less biodiversity it will have. The significance of the lack of diversity, I have no idea. It is easy to speculate that more diversity is a better thing to have, but then it is just speculation.

As for the worm theory....ya got me! But, it makes me think about deep sand beds. If live rock was only a mechanism for increasing surface area for bacterial populations, then I would speculate that a tank could be run with a (large enough) DSB only.

[Ixthys]

Chuck,

I think you may have misquoted me. The rock in my example was at one time LIVE rock, unlike most of the base rock that is sold from a rock quary and may never have been from a coral reef.

I just read your link. I DO believe you have LIVE glass and LIVE plastic. I just don't believe it is enough to handle the needs of your tank by itself.

I would love to know who you buy good quality LIVE rock from. From my experience, most comes from Walt Smith Enterprises, and most resellers act as shipping middle men. For them to open the box and inspect the contents may prevent you from getting a bad batch of rock, but otherwise just slows down the time for you to receive it and get it into your tank. If I could buy directly from Fiji or Tonga, I'd love to know how!

[charlesr1958]

Guess we have different definitions of base rock, I had always bought base rock as dry dead rock as a foundation to put live rock on top of it. But at the same time, a base rock that has been allowed to sit in a tank and gets a bit of algae and such on it is still a base rock to me. And after collecting truly live rock right out of the ocean, it is truly a crying shame that more care could not be taken to preserve the life better, its amazing what a "fresh" live rock consists of as far as diversity of life goes.

Chuck

[leebca]

I feel the same. I miss the live rock we got decades ago. We paid the freight for rock collected in the water, bagged in the water and shipped with the water it was bagged in.

[newtothis]

As you all are discussing rock for an aquarium [salt water] so can I ask what is sand-stone rock and can it be put in a salt water aquarium?

[leebca]

Yes. Our discussion is about saltwater aquaria.

Sandstone rocks are sedimentary rocks made from small grains of the minerals quartz and feldspar. They are, as the name implies, grains of sand stuck together.

I don't know their suitability for the marine aquarium. As a sedimentary rock it can contain a variety of impurities which could harm the aquarium livestock. If it is 'pure' it should be okay, since its basic make-up is conducive to the marine environment.

[philolsen]

Leebeca,
Can you tell me where you got the info that base, DIY etc. rock can never become LR and the life from in the rock can not move to other rock, I have read a lot of people who say it can

[leebca]

The reason why some marine micro lifeforms do not reproduce in our aquariums is the same reason that some marine fishes won't reproduce in the aquarium. That is: They have life stages that require the nutrients and the environment of the sea.

If you review articles by Dr. Ron Shimek you'll learn about the larval stages of worms and various micro fauna and how they don't reproduce in the home aquarium. Such life forms take up residence in rocks found in the sea, reproduce through stages in the sea, and spread. They don't move from rock to rock, but rather go through stages in an environment (the sea) not found in the home aquarium.

Even some snails won't reproduce in the home aquarium to grow up to adult snails. They may move around, may even lay eggs, but they need replacing when they die.

When people generally extol that dead rock can turn into live rock by placing live rock next to it, the life that does move include the algae (coralline, included), many of the microcrustaceans (pods), and the surface organisms (some sessile animals that will reproduce in the aquarium, and non-sessile animals (e.g., anemone) that will actually move on their own).

Part of the erroneous 'belief' comes from people thinking that their home aquarium is a piece of the ocean. Not at all. We mimic the ocean when it is suitable for the husbandry; we alter the system to account for it being closed and much, much, much less diverse.

Thinking about it in commercial terms: Why are we still buying live rock? Why then have rock farms? Why don't we all start selling it? There are tens of thousands of ocean acreage set aside to grow live rock from dead or artificial rock. If dead rock can turn into true live rock in our aquarium, then who needs to import it? Wouldn't we all be selling it?

I think a fine example of what true live rock and rock sitting next to it in an aquarium can and can't do is to do the test. After the person thinks that the dead rock has turned into live rock, take that 'new live rock' out and use it alone in an aquarium startup. This rock will provide the surface for nitrification, but how much denitrification will it perform? The point to this is that true live rock performs denitrification, as does a deep sand bed and other accessories. But the dead-rock sitting next to live rock doesn't come close to doing this. It is still somewhat of a mystery, but we do know that not all life found in true live rock from the sea can move around.

This is not to say that dead rock next to live rock is undesirable. If the aquarist needs or wants denitrification in the home aquarium from rock, then the aquarist has to provide live rock, not dead rock sitting next to live rock. Since nitrates are not that important to a FOWLR aquarium, live rock really isn't needed for such setups. In this instance, the use of rock I call base rock is good enough. In a reef aquarium where nitrate control could be essential to the husbandry, a means of denitrification is needed and that includes true live rock, deep sand beds, reactors, macro algae growth (refugium), etc. My 700+ gallon system is setup with base rock. Why do I need rock from the sea?

Dr. Ron Shimek has written many good articles on the micro fauna of the ocean, their life, identification, and husbandry. There you will find how some life forms in and on live rock don't reproduce or spread in home aquarium from live rock to dead rock. You may want to browse through some of his writings:
Online Articles

[leebca]

Sorry philolsen, it took me a while to dig out my references.

Most of the animals that would be living in the rocks and causing water movement by their activities are polychaete worms of several types. These are worms that live in burrows in the rocks that they may construct, or in pores in the rocks that they occupy.

The worm array is very diverse. In some studies about 30 years ago 2 researchers were able to find 864 worms from 35 species in a small rock with about 53 square inches of surface area; in other rocks comparable values were found. By and large these are worms that are filter feeders or scavengers. By moving in and out of the rock, as they feed, they pump water into the rock. Additionally, they also simply pump water into their burrows to ventilate their burrows so they can breathe.

This diversity just can't be found in the rocks sitting next to live rocks in our aquarium. This diversity does not move to the new rock. The rock next to live rock will still perform nitrification and some denitrification, but will never equal the ability nor diversity of the real live rock.

In addition to Dr. Shimek's site and articles, references listing the worm species found in the rocks are:

Kohn, A. J. and M. C. Lloyd. 1973a. Polychaetes of Truncated Reef Limestone Substrates on Eastern Indian Ocean Coral Reefs: Diversity, Abundance, and Taxonomy. Int. Revue ges. Hydrobiologie. 58: 369-399

Kohn, A. J. and M. C. Lloyd. 1973b. Marine Polychaete Annelids of Easter Island. Int. Revue ges. Hydrobiologie. 58: 691-712.

To get information on their reproduction of these worms, you can check out:

Fauchald, K. 1977. The polychaete worms; definitions and keys to the orders, families, and genera. Natural History Museum of Los Angeles County. Los Angeles, CA. 188pp.

To find out what they eat and other aspects of their habits cross reference the species or families in the first articles with this article:

Fauchald, K. and P. Jumars. 1979. The diet of worms: a study of polychaete feeding guilds. Oceanography and Marine Biology Annual Review. 17:193-284.

[mad_dog01]

Leebca,

Very informative acticle....thanks!

[philolsen]

Thanks Lee,
Have you read this study as well?

http://www2.hawaii.edu/~delbeek/homerf1.html

[leebca]

Thanks philolsen. You refer to the link as a study, but it is an article of opinion of Charles Delbeek. I'll take a look at it.

I forgot to remind you of the information provided earlier in this thread which I quoted from Dr. Shimek.

[agroservicios]

Hi, when reading through the discussion about live rock I feel that the general feeling is "the fresher the better". Question, can I just pick out live rock from the ocean and just put it in my tank as is? I live right at the Pacific Ocean and would be able to pick out many a piece of live rock however I have read many times as well as heard that when you do that the possibilities of introducing unwanted inhabitants is enormous and possibly very dangerous for your existing population. (I do use fresh seawater for my water changes and would like to use live sand as well.)

(I am new here, and I see thread is already old, but hope to get some answers)