A definition for " live rock".

Belgian Anthias

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In order to make it possible to distinguish and compare we must define what is considered “living stone”, we must define being alive. Any piece of rock placed in a biologically active medium, such as an aquarium, will soon become “alive”, covered with life.
To me, "living rock" is a piece of rock covered with what is called "periphyton" or "aufwuchs", it is covered with a mixture of dead and living growth of all kinds of organisms. The stone is covered with microbial mats, microbial communities. The added value must be sought in the origin of the stone, as it is transported over very long distances.
It is clear that when one speaks of “living rock” in the literature, they don't always talk about the same thing, especially when referring to “treated living rock”, so-called “cured live rock”.
A piece of living rock that meets my definition can therefore just as well be a piece of rock that has been in an aquarium for some time and has not been overgrazed. For my definition, porosity plays little or no role. The surface actually useful for biological processes is compared.

It would be interesting to know what is your definition of " live rock" and what would be the added value of such rock compared with my definition.
 
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EMeyer

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I define real live rock as coral skeletons bearing a microbial community from the ocean.

Rocks can deviate from this definition in some ways and still retain some value. But if its not porous coral skeleton, or doesnt have a microbial community from the ocean, IMO its not "real" live rock.

All the coralline algae and worms and stuff, I doubt this matters for much other than appearance.

Porosity and a diverse microbial community are the desirable features.
 
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Belgian Anthias

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Porosity? Must porosity be part of the definition of "live rock"? And why?
Can it be classified in porosity-classes I; II; III. Compared to GAC?

I know porosity is often linked to a certain denitrification capacity. Even when it does make a difference for the total denitrification capacity of the system, positive or negative, denitrification does NOT support the carrying capacity of the system. Heterotrophic denitrification is the anaerobic remineralization of organic material.
 

homer1475

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To me, it is something we took out of the ocean and didn't do any silly things to. :p
100# agree.

Those large vats of white rock in water we see at the LFS is not live rock IMO.
 
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lapin

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Good thread
I think there should be a chart for rock types as people get them a bit mixed up. Life and Live are not the same

Here is a partial list;

Dry
Dead (with junk on it)
Tanked (fake resin insert rock formation with rubber corals)
Life (dry with bacteria sprayed on it)
Cured
Live
 
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Belgian Anthias

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Rocks and stones do not live, what grows on it represents life. I used the term " living rock" to form my definition which seems to me not correct. if I use" life rock" the spelling correction wants me to change it in " live rock" which for me, a Belgian speaking Dutch, seems not correct for pointing out " rock which is covered with ocean life". So, I will use "life rock".

Is cured rock still "life rock". Are there any limits or and rules for transportation duration and condition?
 

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I feel the greater porosity could increase the "grade" of the live rock. Remember back in the day when people debated about "quality" live rock from the ocean whether is was dense Carribean rock or light Pacific rock?

Live rock to me has to have microbial/coralline/sponge, etc life forms on it or in it. I don't care where it got that life whether it was in Fiji, Florida or some old established land based system.
 
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Belgian Anthias

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I feel the greater porosity could increase the "grade" of the live rock. Remember back in the day when people debated about "quality" live rock from the ocean whether is was dense Carribean rock or light Pacific rock?
Why porosity should be part of the measure for determining the grade of quality?

How porosity may influence the quality of the rock?

For example, GAC has different grades and can be classified by its porosity. The porosity can be measured. A lot of research has taken place concerning GAC, not only as an absorber but also about its capacity as a bio-filter. About "live rock", no such research is available.
1L of good fresh GAC can contain +- 90ml water.

I think the specific gravity cannot be used to determine the porosity of "life rock" as life, filling up the pores, is part of the weight, is part of the density.


Dens or light? Quality rock is transported ASAP. Weight makes a big difference if transported by air, a good reason to promote light rock.
Hollow rock or porous rock? Are the pores and hollow chambers interconnected?
Aquacultured rock?
Cured rock?
 

fish farmer

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Why porosity should be part of the measure for determining the grade of quality?

How porosity may influence the quality of the rock?

For example, GAC has different grades and can be classified by its porosity. The porosity can be measured. A lot of research has taken place concerning GAC, not only as an absorber but also about its capacity as a bio-filter. About "live rock", no such research is available.
1L of good fresh GAC can contain +- 90ml water.

I think the specific gravity cannot be used to determine the porosity of "life rock" as life, filling up the pores, is part of the weight, is part of the density.


Dens or light? Quality rock is transported ASAP. Weight makes a big difference if transported by air, a good reason to promote light rock.
Hollow rock or porous rock? Are the pores and hollow chambers interconnected?
Aquacultured rock?
Cured rock?


Obviously quantifying porosity of an eroded coral skeleton from different sources with attached organisms would be much different that a manufactured product like GAC.

Generally what I have heard for years is highly porous rock is better for filtration than say granite.
 

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I'd call "live rock" any rock with a diverse, live bacterial biofilm. However, quality can vary.

For instance, I originally set my tank up using CaribSea Life Rock. That stuff is like concrete--there is no way that it can sustain the quantity of bacteria (per pound) that real coral skeletons/more porous rock can. After switching to more porous rock/dead coral, my tank is having fewer issues with algae and nutrients, possibly because the bacteria is outcompeting the algae for nutrients.

Also, quality need to take into account diversity (i.e. from the ocean vs. bottled/sprayed on bacteria)
 

HuduVudu

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Live rock is what I have in my build thread. It is pulled from the ocean and put in your tank. Cured live rock is rock pulled from the ocean and put in a tank to let the die off of organisms happen someplace other than your tank. If you ship and collect the live rock quickly enough then the cure would be considered instantaneous. Live rock is NOT JUST bacteria.

Life rock is brand of dead rock infused with bacteria from CaribSea. The name is a marketing ploy, and doesn't really make sense in English (live rock makes more sense but is also a misnomer).

I think that most people have never really experienced live rock and are therefore confused about the original intention of the name. I think marketers take advantage of this confusion.
 

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Porosity matters a lot to me too. The lighter the rock, the better it has been in reducing nitrate and allow microfauna to populate different levels. The biggest difference that I can think of is the old Marshall Island rock where a basketball sized piece could be 5-6 pounds if you let it sit out of water for a few minutes vs a basketball sized piece of older Caribbean Quarry Rock that was placed in the ocean for a few years that might be 20-25 pounds. That 5 pound piece of MI rock could keep some nitrates down where that 25 pound piece of solid limestone would struggle even though both could get coralline on them.

I also don't want rock covered in purple epoxy where nothing can get into the pores to live and work.

I also want the rock to be phosphate free and not a reservoir that will take me a 5g bucket of GFO to remove all of the bound phosphate from it. This falls into the category of "did not do silly things to" as mentioned above.
 

Eyesac

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These from Gulf Live Rock and Tampa Bay Saltwater. Living in Central Florida is not bad. Three hour round trip by car for TBS today actually and the GLR was shipped Monday and delivered Wednesday.

20201119_093419.jpg 20201120_162739.jpg
 
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Belgian Anthias

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In my opinion, most filtration takes place on the visible surface, in good contact with the water, having a sufficiently high water exchange rate.

Deep in pores, most likely only sulfate reduction takes place as on the spot no or very little nitrate may be available.

That is why I did do not take porosity into account to form a definition.
 

HuduVudu

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In my opinion, most filtration takes place on the visible surface, in good contact with the water, having a sufficiently high water exchange rate.
What about the planktonic uptake in the water column? Most live rock has some sort of bivalves, if they survive what about them? Macro algaes? Micro fauna? These all "filter" the water to some degree or another. That is why live rock works so well, because there are multiple avenues of "filtration".
 

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Porosity is critical, its why real coral skeleton is so much superior to fake concrete or mined limestone.

Why? Think about it this way. The rock itself is irrelevant and inert. What we are after are the Bacteria and Archaea that make up the microbial community. These live on surfaces, both the external surface and any internal surfaces.

A totally non-porous* rock has effectively zero internal surface area. A highly porous rock (coral skeleton) has literally thousands of times more surface area (**) because of all the internal cavities.

*I only consider pores that are large enough and reach the surface to be worth considering here. Technically concrete is "porous" in that water can soak in. But it doesnt have any internal spaces. Likewise, pumice has internal pores but they don't reach the surface. Coral skeletons are ideal.

** I pulled this number out of the air but I bet its a reasonable estimate.
 

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