By James W. Fatherree, M. Sc.
Answering Some Live Rock FAQs
Live rock is a key
component of a reef aquarium and is used as the base that everything else is
placed upon. It is also being used by more and more folks to build
structures and for decoration in non-reef aquariums too. It can also
easily be the most expensive component as well, so it’s worth your time to learn
as much about it as possible and how to take care of it. That being the
case, I’ve provided some info and answers to a few commonly-asked questions
concerning live rock and what to do with it once you get some.
First of all, what is it?
Here’s a piece of great looking Fiji
rock that is cured, clean, and practically covered in beautiful
Despite the fact
that there are several different types, almost every piece of live rock is
fundamentally the same thing. It's all limestone that has been collected
from various areas in the sea where loose chunks of rubble can be picked up. In
most cases this limestone rubble accumulates in areas naturally, but in others
it has been specifically placed somewhere with the intentions of collecting it
Aquacultured live rock sometimes has a few live corals on it, and other
unique stuff, too. It doesn’t all look this good, of course, but
this particular piece is awesome, being covered by corals, coralline
algae, and sponges.
When it is
collected, these pieces of limestone have all sorts of organisms living on their
surfaces and also within their porous interiors, and this is where the "live"
part of "live rock" comes from. In general, you can expect a significant
variety of microorganisms to populate any given piece of live rock and most will
also have at least some coverage of coralline algae giving it a patchy purple,
pink, and/or red appearance. A large part of what you’ll see for sale has
those minimum inhabitants. On the other end of the spectrum, top-quality
live rock has those organisms and may also carry a surprising variety of
macroalgae, sponges, tunicates, bryozoans, worms, clams, snails, crabs, hermit
crabs, shrimps, barnacles, brittle stars, sea stars, sea urchins, anemones, and
soft and stony corals, etc. Lots of stuff!
How does it form?
variety of creatures in the marine environment use the compound calcium
carbonate to form whatever hard parts they may have. These parts could be
anything from skeletons and broken pieces of them in the case of stony corals,
to spiraling shells in the case of snails, to tests in the case of sea urchins,
to spicules in the case of sponges, etc. Numerous sorts of algae use
calcium carbonate to strengthen themselves or to produce tough rinds on surfaces
as well and there are several types of plankton that use it to build minuscule
containers to live in, too. The list is actually quite long.
They do this by
biologically combining calcium from the surrounding seawater with some carbon
dioxide to form the minerals aragonite and calcite. Some organisms use one
of these calcium carbonate minerals, some use the other, and some use both.
In addition to this biological production of calcium carbonate, when conditions
are right it can also precipitate directly from seawater without any biological
help. Conversely, it can also dissolve back into seawater at times if
environmental parameters change in the other direction. Things like
fluctuations in the local concentration of carbon dioxide and pH can cause this
to happen. And, because the seafloor a dynamic environment, these sorts of
back and forth reactions are occurring at essentially all times on some scale
within various sediments and rocks.
Here’s a great example of the hodgepodge of calcium carbonate materials
that can end up forming live rock. Here we have tridacnid shells, coral
fragments, sand, and more, all of which can eventually be “glued
together” to form limestone.
In a generalized
setting, stony corals build calcium carbonate (aragonite) skeletons, which
accumulate over the eons to form the foundational hard structure of a reef.
Even when corals die these hard skeletons remain. However, the
ever-constant erosive forces of wave activity can slowly break apart the reef
structures formed by corals a little at a time during relatively calm periods
and can also literally demolish large areas during major storms. Thus,
there's more activity going on than just building up and up, as there is a never
ending cycle of building and destroying. It is through this process that
coral skeletons can be drastically transformed over time.
As this is going
on, a myriad of other organisms that live in the reef environment also produce a
constant supply of calcium carbonate that gets added in with corals' skeletal
material. Some of these additions may be as big as a Conch shell, or they
may be tiny calcium carbonate particles produced when calcareous algae is ground
up by predators and waves. Thus, we end up with a hodgepodge of calcium
carbonate bits and pieces created by all sorts of living things, any of which
can be called limestone once the creating organism is dead.
this whole mix of limestone bits and pieces is constantly being bound together
by rinds formed by other calcareous algae. Water parameters change easily
within the pore spaces and voids found between all these things and within them
too. Thus, the non-biologic precipitation of even more calcium carbonate
can form lots of limestone "glue" inside and in between them. But wait,
changes in water parameters can also lead to the dissolution of it elsewhere.
Any of these pieces can be slowly dissolved from the inside out and/or dissolved
away completely. So again, there is a constant cycle going on as new and old
pores, voids, rinds, and glues can be formed and dissolved, formed and
dissolved, over and over and over. Regardless of the details, the net
result is a hard reef structure made of a jumbled mix of biologically formed
pieces and a lot of calcium carbonate rinds and glues that meld much of it
together. It can have a highly variable amount of pore/void space within
it and can be densely colonized by reef organisms, as well.
These chunks of coral were broken away
from a reef by a storm and are the sort of things that often end up being
live rock - if they stay submerged for some time and aren’t actually blown
out of the sea.
Moving through time
as the reef is broken up in some places, pieces of this limestone of variable
size are freed. These pieces can be rolled around, broken up further and
abraded by sand. They can be worked over by all sorts of biting, boring,
and burrowing organisms and are colonized by various others too. And, as
mentioned before, they can also be affected by ever-changing water chemistry.
The net result is that in certain environments very diverse looking broken away
pieces of limestone can end up at rest on the surface. Such a piece may
have had some life on it when it broke away or may be colonized by organisms
afterwards or both.
Live rock can also
be produced by taking limestone mined from land, dumping it in the ocean in an
appropriate location and waiting for it to become colonized. This is
called live rock aquaculture, and several businesses that are doing it use
quarried limestone pieces from areas that were submerged in the past. Even
though they’re just plain limestone rocks in a pit now, that rock was formed by
marine organisms and processes in the geologic past and stranded on dry land by
changes in sea level or changes in the earths surface.
these pieces of ancient seafloor are carried out on boats and barges to
predetermined areas and dumped to form small man-made reef structures.
Eventually they are colonized by the same sorts of things that would be found
living in and on any other piece of limestone in a natural reef and can be
collected and sold.
Where does it come from?
Live rock has been
collected in a number of places but most of it comes from islands in the South
Pacific. The majority originates from island nations like Fiji, Tonga, and
Samoa. There are two primary reasons for this. First, the collection
of live rock in U.S. waters was banned by the government in 1997. Second,
it's cheap. Island workers will work for much less than U.S. workers and
since airplanes fly to the islands loaded with supplies and fly back relatively
empty, air freight out of the islands is reasonably priced.
government may have banned the collection of "wild" live rock, they decided to
allow businesses to make their own and collect it. So, aquacultured live
rock, which is produced almost exclusively in the Gulf of Mexico and the Florida
Keys has made its way into the market with all of this Pacific rock. The
result is a variety of live rock types from a variety of areas to choose from.
Is one type better than another?
This is one I can't
answer for you, as there certainly is no single "perfect" type, and it's hard to
even proclaim that one is better than another. However, I can help you
make your own decisions. The key is to think ahead about what you want
your aquarium to look like and how much you want to spend.
There are different
types of aquacultured live rock, some better than others, and in general it
typically has the most live stuff on it. In fact, the best rock is
actually completely covered by coralline algae, encrusting sponges, and corals,
etc. This can be great looking, but at the same time, if you are building
a big rock structure/wall you will inevitably end up having to stack many pieces
in such a way that much of what's on it will be squished and killed. As a
general rule, aquacultured rock is dense and has bouldery, less interesting
Here you can see the difference in the
porosity of some typical Pacific live rock (top) and some Florida
aquacultured live rock (bottom). The Pacific rock is much lighter for
its size due to all the pore spaces, while the Florida rock is relatively
dense and heavy.
On the other had,
most wild Pacific rock has less life on it because of the greater time spent in
shipping and handling, but what is there is tough! Wild collected Indo-pacific
rock is usually less dense than aquacultured rock and has some especially
interesting shapes, too. So, it might not be “alive enough” for you to
build your whole structure with, but some pieces are so neat looking that they
make great additions anyway.
There are other
sorts of more unusual "specialty" live rock, such as “Tonga branch” rock.
It looks just like the name sounds, as it is made of broken up pieces of
staghorn coral that have died, been physically and chemically altered, and then
overgrown by coralline algae. Thus, it has a very distinctive form and
doesn’t really look much like a rock at all. You could, of course, use
just Tonga branch to build your whole reef structure if you so desire, but many
hobbyists prefer to only use some pieces here and there if they use any at all.
In such cases some other type of live rock is used to make the base structure.
Each type can be
used to achieve a very different look. Aside from that, you need to keep
in mind that none of it is cheap, and you will have to compromise between good
looks and function versus using the least amount of live rock to do it. You have
to buy the stuff by the pound, so fewer pounds means more money left in your
wallet (or purse).
Thus, there's more
to think about than just looks. Most Pacific rock is relatively porous and
lightweight and has lots of open shapes, especially compared to aquacultured
rock, so fewer pounds are needed to fill a tank. In fact, if you arrange it
right, just a few big pieces can really fill a lot of space and look great. On
the other hand, since aquacultured rock tends to be less porous and can be
relatively heavy, it takes more pounds to fill the same amount of space.
Keep in mind that aquacultured rock typically has much more life on it!
Since the number of pounds needed can be significantly different based on which
type you choose, the price per pound may be less important than the total cost
of your choice.
Some businesses keep lots of rock
stocked in their own systems long enough for it to cure before you get
it. In these cases, you might be able to add it to your aquarium
immediately, although it may still be prudent to hold it in quarantine
for several days just to make sure it is okay. Sniffing it can
help you decide.
In case you aren't
thoroughly confused, "base rock" is often available too. Typically base
rock is also limestone rubble, but it generally has next to nothing or even
nothing living on it, with the possible exception of some microorganisms.
It may even be sold dry. Base rock is much cheaper than other rock and
using it to build the base of your live rock structure is a great way to cut
costs. Just buy a few pieces and then cover them over with quality live
prefer to get the "best of all worlds" by mixing any or all of the types of
rock. A foundation of base rock, a few pieces of top-quality aquacultured rock
for lots of life, and pacific rock and/or branch-type rock on top for
looks. You have to decide, but you certainly shouldn't feel like you have
to pick just one type.
How do you take care of it once you have it?
When you get fresh live rock you’ll need to keep a watchful eye on the
attached organisms, such as this clam and encrusting sponge, from start
to finish through the curing process. If they should die, remove
them manually immediately.
Once live rock is
collected, there is always at least some die-off of the life that is on/in it,
and sometimes there's a lot. If you happen to get some rock that has been
collected very recently, you'll have to deal with this die-off yourself.
On the other hand, if the rock has been sitting in a well-maintained dealer's
system for a while you may not need to do anything but put it in your aquarium.
Regardless, after it is in your tank, you'll still need to do a few things to
keep it looking its best. So, let's keep going.
Many sponges and
other organisms found on live rock cannot tolerate shipping very well because
they are exposed to air and/or unacceptable temperatures in the process.
Thus, many things on live rock will die and rot away within a few days of being
collected and transported. There may also be numerous things living inside
the rock that die and decay, too. Such decay, whether you can actually see
it or not, produces ammonia in aquariums and ammonia is deadly. It takes
some time for all this to happen and for the decay process to stop, thus you
typically can't just buy a bunch of live rock and add it to a stocked aquarium
or add livestock to an aquarium you have just added fresh live rock to.
So, what do you do?
You "cure" the rock. Typically, this means keeping the live rock
quarantined in a tank without other livestock, and maintaining good water
quality in the tank for at least a couple of weeks. Even longer is better
if you have the patience.
The best way to
start the curing process is to half-fill a bucket with saltwater and vigorously
shake off each piece of rock in the bucket when you first get it home.
This will help to clear off any sediment and loose dead material. Be sure
to look over each piece to see if you can spot anything that obviously needs to
be removed, like a sponge that has white gunk and bubbles on/in it, or a dead
clam, or whatever. Then, add the pieces to a quarantine tank or tub of
saltwater that has strong circulation, but isn't well lit (unless you have live
corals, etc. on it) - and wait. How long? At least as long as it
takes for things in/on the live rock to stop rotting.
Editors note: [Live rock often has sharp edges or animal shells, and in rare
cases, animals that can cause injury. Wearing heavy rubber gloves when
handling live rock is a very good idea!]
If you’ll maintain an adequate
concentration of calcium in the water, acceptable alkalinity levels, and
good water quality, you can expect colorful coralline algae like this to
slowly grow over practically every inch of your live rock.
Use a good skimmer
on the container and test for ammonia, too. It is also very helpful to
employ a good biological filter that already has a full complement of bacteria
if possible. Something like a bio-wheel filter or canister filter with bio-media
will usually be fine for small batches of rock, but I've used big fluidized bed
filters, and even trickle filters for big lots of rock. Do note that these
should already be established though.
If ammonia shows
up, do a large enough water change to get it as close to zero as possible.
You need to do this because if you let ammonia concentrations get too high it
will kill everything else on the rock that isn't already dying, which will make
the curing process last even longer and very likely leave you with some base
rock that is devoid of anything but bacteria. The best thing to do is keep
up the water changes as needed until no more ammonia shows up. Of course, this
is unfortunately the most expensive and time-consuming way too, but it also
helps maintain calcium, alkalinity and general good water quality.
necessarily done when ammonia stays at zero, though. This is because there
are almost certainly some bacteria living in the rock that can consume ammonia.
So, if the bacterial population increases in size until it can remove ammonia as
fast as it is produced, you may get a zero reading before the rock is really
finished with its die-off period. Thus, your nose is often the best way to
determine if you are really done or not.
When ammonia stays
at zero, start giving some individual pieces a good going-over with your sniffer
every few days and see if they stink. Fully cured rock has a clean
"oceany" smell. If they stink, then things are still decaying - even if
your ammonia test kit says things are fine. Get it? So, when ammonia
is at zero and
things don't stink, you really are done. If you manage to get to this
point in less than a couple of weeks I suggest you wait it out a little longer
anyway just to be safe. Then, after the waiting has gone on for what seems
like an eternity, you will finally be ready to use your cured live rock.
Now, with all that
covered, you should also keep in mind that if a dealer has had the live rock in
their own well-maintained system for a while, the whole curing process may have
already been taken care of for you. You may get to skip it all.
Yippee! Thus, you may be able to pick up the rock, take it home, and add
it to your aquarium immediately after acclimation.
If you think this
is the case, use your nose again first and see how the pieces smell. If
they have been in the dealer's system for at least a couple of weeks and there's
no stinky odor, it should be okay to add it to your aquarium. I do treat
the pieces just like any other livestock and slowly acclimate them to the new
water conditions first, though.
Of course, each
situation can be a little different, so in the end you have to make your own
judgment call when it comes to curing or not curing live rock. But, as is
often the case, if you have any doubts it is best to show a little patience and
play it safe.
Other than getting
it in the tank, you’ll want to use calcium additions to keep the calcareous
coralline algae growing, and to help it spread over areas of the live rock that
aren't covered already. Like corals and other calcium
carbonate-precipitating organisms, this requires an adequate concentration of
calcium in the water, acceptable alkalinity, and good water quality, too.
If you'll do all this, given enough time your live rock can become completely
encrusted with living things, and will look absolutely beautiful.