Can Live Rock "Wear Out"?

[GaryZ]

The live rock I have in my tank has been around for quite awhile. Is there "lifespan" for live rock. Does there ever come a time when live rock becomes depleted. Since I don't fully understand the concept of live rock, and I see people mention "die off", I can't help but wonder wether or not live rock, left in a tank with only a few fish and little light, will eventually become depleted and useless.

[charlie]

I have read where people change out a portion of their liverock every year or so to keep populations fresh. I can see their thinking, I just can't afford to do that!!! I think that there might be a lifespan to rock, but I really have no idea what it is.

[yankeebobo]

If you leave the LR in a tank with little light and fish only, then there is always a potential to some die off. One of the things that keep live rock going is the life cycle. LR will feed off some chemicals that you may be dosing, light, etc. I am sure others will certainly offer more certain info. Based on the knowledge, LR in a reef tank would contain more life to sustain itself with the proper lighting than LR in a FO tank. In a FO tank, you may not dose or keep the light on as much as a reef.

[zhenya]

Not to ceate more confusion or anything, but please give this article a read over. I am sure it will help you to understand how live rock works and what it is that really makes it a "live" rock, suitable for our needs as a filtration media located right in the tank... ;)
http://reefkeeping.com/issues/2004-0...ture/index.php

[Samper]

I will say that to keep my tanks as diverse as possible I rotate the LR that doesn't have any corals on it around piece by piece throughout my systems. I also every now and then take a piece that's overgrown with zoanthids and trade it for another rock of equal size and possibly get a new coral or two out of the deal. I think this helps me keep a high level of biodiversity.

[GaryZ]

Thanks for the link, I'll read it when I get a chance. My tank is gonna be FO for only about another 3 weeks. Then I'm gonna slowly start introducing easy corals. I guess I'm just wondering if depleted live rock can be replenished. Hopefully the article will clear it up.

[64Ivy]

I am no scientist, nor do I play one on TV but, imo, it only makes sense that eventually LR would get 'full' and start to lose its denitrification abilities. After all, sandbeds can get full and LR is just sand that hasn't worn down yet, right?

I recently had a fairly minor phosphate problem which was localized around a single piece of LR. Unfortunately, a couple of my favorite SPS corals happened to be growing on that piece and were subsequently lost. Examination of one of the skeletons revealed a greenish tint inside...evidence of poisoning from the 'wicking' of phosphate leaching though the rock. (Many of the larger rocks in my tank are nearly 10 years old, btw, and I also feed like a pig.) So how am I handling it? More aggressive tank maintenance by way of wetter skimming, ozone, blowing debris out of the rockwork more often and more frequent water changes.

If you have the time and patience, you could always cook your rock. I probably would if I was starting from scratch (and were single ) But in my position, a little better husbandry is the best I can do. Good luck.

[GaryZ]

I've seen the term "cooking rock" alot. What does it mean and what does it accomplish?

[CSeaSee]

From what I know, people cook (boil) their rock to get rid of unwanted critters, like a really bad case of hair algae. Of course, this is a nonselective process, and it'll kill off just about everything , except some spores of various organisms. The rock is essentially dead at this point and needs to be reseeded.

I don't think the denitrifying ability of live rock wears out. The bacterial populations will grow until they reach a maximum density, and at that point the new bacteria being created will replace the ones dying and the population will stabilize. This is called S-shaped growth- the growth of any population plateaus after an exponential phase. Graphed, it looks like a "S." The time it takes any populaton to plateau is highly variable and depends on a number of factors, such as total available food and space. In home aquaria, if the live rock is being replaced every now and then, the rock's bacterial population may never reach its plateau phase. One other thing to note is that if you have a stable population of bacteria in your tank, and something happens to drastically increase the food available to them, like the death and decomposition of a fish, the population of the bacteria will spike, and then crash when the extra food runs out. Once the bacteria crashes, it sets off a chain of events that can really screw up a tank, because a significant portion of the biological filter is dying because it became severely overpopulated, and is now starving. This is one reason why dead things can be so bad for a tank. There's a lot more to growth then that, but it's a pretty good overview. In a nutshell, live rock's denitrifying ability often gets better over time, as bacterial population recover from the stress of being collected and shipped. As far as buffering capacity and the purely chemical side of live rock, maybe someone who majored in chemistry (instead of biology) can chime in about that. I know that sand probably works better at buffering than live rock because of a relatively high surface area- to- volume ratio.

Wow, I wrote a lot. I could probably use this in a paper for some class...

[inwall75]

LR will last forever. However, it can get so dirty temporarily that a lot of bad things can come out of it. Problem algaes, phosphate wicking into SPS, etc. That's because we put way to much bioload on them.

If you have a REAL bad problem with nasty algaes, you can boil them outdoors for a couple of hours. Use RO/DI water because the low pH of the water will cause the phosphates to de-adsorb. Eric Borneman had a friend try it indoors one time and something aeresolized and made them sick so always do it outside.

Cooking LR is very different from boiling LR. It basically involves putting LR into a container with no lighting, a heater AT NORMAL TANK TEMPERATURES, a protein skimmer (if available), and a powerhead. The bacteria will clean the live rock out for you. It takes quite some time if your rock is real dirty. As the rock sheds, you will have to turkey baste the rock and siphon up the detritus. You also have to do periodic water changes. Basically you keep this up until detritus stops leaving the LR. Other people use more than one tub. They fill up the second tub with fresh saltwater and then "dunk and swish" in the old water to remove the detritus from the rock and then move it to the new tank. They then wait a week and repeat with fresh water in the 'former' old tub. Depending on how filled the rock is with detritus, this process can take one month or three or four.

Zhenya,

RC is down right now so I can't read that article. However, if that article is that ridiculous monstrosity that Dr. Ron wrote fairly recently, I have plenty of comments.

[CSeaSee]

Thanks for explaining the cooking vs. boiling!

[zhenya]

Zhenya,

RC is down right now so I can't read that article. However, if that article is that ridiculous monstrosity that Dr. Ron wrote fairly recently, I have plenty of comments.

Well, here's the links to some of the the threads about this subject that you couldn't get to on RC.
http://reefcentral.com/forums/showth...hreadid=437342
http://www.reefcentral.com/forums/sh...t=cooking+rock

and, I am not so sure what "monstrosity" you are refering to but I've never felt this strongly about any of the articles I had ever read written by Dr.Ron or any other author for that matter.
As far as your comments, you are free to express them in this thread, as long as they are civil and on the point... ;)

[inwall75]

Please don't misunderstand me. I'm not anti-Shimek. I've personally spoken with him several times. However, he is interested in bugs and worms and alway tries to relate everything in saltwater back to them whether it is true or not. RC is back up and that IS the article I was assuming the link was to.

I'm not kidding here. When I first read it, my first thought was that Dr. Shimek had officially gone insane. Worms are what move the water through the rock instead of Van der Waals forces, viscous-entrainment, bernouli principles, and last but CERTAINLY not least...bacterial biomass movement? Sure their movement helps but their help is miniscule in terms of water movement.

He also claims coralline algae blocks the pores and ruins the rock? How are our coralline covered reefs surviving? How big do the holes have to be? A significant part of much of live rock is decades worth of coralline algae deposits on top of coral skeletons. In other words, the the reef is nothing but coral skeleton and coralline algae.

I know of rock boring sponges, urchins, clams, algaes, and bacteria that dissolve LR and all of their actions create holes. However, a large proportion of the pores were from the fact that most of it was created by coral skeletons which are not solid but are quite porous all on their own. In addition, much of it consists of many skeleton held together by coralline.
Regardless, coralline is not impermeable. The thalli fuse together but it isn't a complete fusion. Just because we can't see a pore doesn't mean that water nor bacteria can't go through the microscopic pore. Take a look at these microscopic images of coralline. Thallus Organization (PS....look at the links on that last link too).

He is using data from 1955 when we didn't understand hardly anything regarding reefs. (I'm not saying it's invalid, but I have to question why more recent research wasn't used). However, that's minor. My main issue is that after discussing all of the ancient algae data in the article, how does this data relate to what we are really talking about...Biological filtration. Since Biological Filtration is done by bacteria, why does the article gloss over what bacteria really do in LR? I'm guessing that he doesn't believe the info that the people who invented the Berlin Method and brought reefkeeping to the masses were wrong when they added live rock and saw denitrification.

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.

Well at least he said one smart thing. This is why I recommend that people cure their LR in a separate container if they want a DSB...why fill it up with detritus any quicker than it needs to be filled up.

To sum it up, I have read that article and I have a few problems with his line of thinking. If what he was saying is true, then I better start buying worms to add to my Granular Activated Carbon to make it work. Activated carbon is used in the food industry, chemical industry, etc. because there is a method of things getting inside small pores.

I'm going to concentrate on Viscous Entrainment and Van der Waals forces here because it will help people understand a little of both GAC and LR. That is most certainly not the only way that water enters LR but it's hitting two birds with one stone. We like the more porous live rock because of it's increased potential for biofiltration. We like the more porous GAC because of it's increased potential for filtering as well.

Here's the basics on how carbon works and LR functions in a similar manner. A single pound of activated carbon has the surface area equal to 125 acres. Very porous stuff. It has been baked in such a manner as to create all of the different types of pores and surface area.

TRANSPORT PORES---Transport pores are the internal volume of the carbon granule where the graphitic plates are far apart or the cracks and crevices of the particle. The transport pores act as the "highways" for the contaminants to reach the adsorption pores where they are adsorbed. It is important to note that no adsorption takes place in the transport pores. Transport pores are vitally important, as they allow access to the adsorption pores - especially those deeper within the carbon granule.

Basically the bigger holes.

ADSORPTION PORES---Adsorption pores are the internal volume where the graphitic plates are very close together creating a higher energy. Higher energy is important to adsorption because it is the energy that "holds" the contaminant (the carbon "adsorbs" the contaminant). The volume where the graphite plates are far apart and the cracks and crevices make up the transport pores. It is important to note that all adsorption takes place in the adsorption pores and not the transport pores.

Basically the smaller holes.

VAN DER WAALS FORCE---There is a natural attractive force between all things in the universe. Gravity is one of these forces. In adsorption theory, the force between the contaminate and the carbon is the adsorptive force. It technically is a Van der Waals force. It is this attractive force that enables adsorption to occur. The forces are a function of the distance between the two objects. The closer together the objects are, the higher the attractive force is. The higher the attractive force, the higher the "energy" level of the pore space.

Basically, this is one of the ways that Phosphates are adsorbed onto LR (and into LR). Van der Waals forces are exactly how a protein skimmer works as well.

HOW DOES CARBON BIND THE CONTAMINATE----Once the contaminant enters the carbon granule via the transport pore space, it diffuses into the carbon matrix until it enters the smaller pores where the adsorptive forces begin to take effect. Once it reaches a higher-energy area, it can no longer migrate (or diffuse) because the adsorptive force is stronger than the diffusional force. The contaminant is adsorbed to the carbon surface by the adsorptive forces (the Van der Waals forces). In this state, the contaminant is referred to as the adsorbate.

That's only one of the ways how water and other compounds get into the live rock....worms do it too somewhat.

All of the above completely ignores the fact that bacteria not only migrate to appropriate environments, THEY ARE CAPABLE OF CREATING THEM. Go look through the front glass of your tank. Denitrification is occuring in a biofilm so thin that you can look through it. It's certainly not enough to successfully maintain a typical bioload of reef tanks but it is happening.

[Ninong]

The article zhenya was referring to is entitled Live Rock as a Biological Filter: Hit or Myth? and it was published in the May 2004 edition of Reefkeeping. http://reefkeeping.com/issues/2004-0...ture/index.php

[Ninong]

He also claims coralline algae blocks the pores and ruins the rock? How are our coralline covered reefs surviving?

Coralline algae play a key role in the consolidation of natural reefs. They deposit in their cell walls a mixture of calcite plus 25% MgCO3. After the death of their cells the crystallization of both of these carbonates continues in them. This process results in the lithification of their colonies and thus in the building up of the flat rocks. The branching corallines, which grow on the pieces of coral rubble, also finally cement them forming solid rock.

What we call "live rock" is actually coral rubble. We use it as a filtration medium in our marine aquaria. Lithification of Corallinaceae on the surface of this "live rock" would be counterproductive to goals we hope to achieve. Obviously this is not a concern in the natural environment since the area beneath the coralline algae plays virtually no role in the processing of nitrogen.

[CSeaSee]

So following this up... coralline algae growing on our live rock is a bad thing? That flies in the face of everything I've heard and read.

[inwall75]

So following this up... coralline algae growing on our live rock is a bad thing? That flies in the face of everything I've heard and read.

No worries. Our tanks are NOTHING like natural reefs. We don't have 100% waterchanges several times per day, we don't have periodic upwellings of waters, we don't have complete restarts that major storms provide, etc., etc., and so on. Unfortunately, we also don't have abyssal plains to sink our detritus in whereas the reefs do.

Natural reefs don't take care of excess nutrients the same way we have to. Don't worry about coralline. My disdain for that particular article caused me say statments that overreached somewhat and Ninong called me on it. In spite of my overreaching, I still maintain my opinion of that article.

[Ninong]

So following this up... coralline algae growing on our live rock is a bad thing?

It's a natural thing. I have lots of it on the live rock in my reef aquarium. I like it. I also have a deep sand bed. I like it, too.

Dr. Ron Shimek, in an article that zhenya linked, proposes the possibility that the growth of coralline algae is deleterious to the functioning of "live rock" in an aquarium as a filtration medium. I don't think I'm ready to express an opinion on that proposition one way or the other.

[CSeaSee]

Got it...

[Ninong]

We cannot possibly duplicate the nitrogen processing capabilities of the natural reef, so we use artificial means to achieve the same ends. Some of our artificial means may even seem "natural," but that doesn't mean that that's how it's done in nature.

For instance, we don't have phytoplankton and bacterioplankton in our water column like the natural reef does to consume inorganic N and P.

We don't have the lush growth of macrophytes and periphytes on the surface of the reef to process nitrogen. We don't have the same benthic epifauna either. Nor do we have the same hydrodynamics or thermohaline capabilities. We don't have the same water currents, wave stresses or periodic sea level oscillations caused by the tides.

Nor do we have the same dillution factor. In fact, there is precious little of the natural reef environment that we can duplicate in our little glass boxes.

The reason that some folks have disagreements with Dr. Ron Shimek is that he frequently writes articles based on valid natural reef processes and then tries to apply these directly to hobby marine aquaria. Many folks will find his various propositions difficult to accept based on their own personal observations. Perhaps sometimes they have a point. Perhaps sometimes they don't.

After Dr. Rob Toonen published his most recent study on nitrification and denitrification in various sand sediments in laboratory marine aquaria, I have given up trying to make sense of certain aspects of this hobby. The conclusions of that study contradicted the previously held conventional wisdom of a lot of people, including Rob Toonen.