Live rock is the ever-present structural foundation for essentially all reef aquariums, and it is also used by a large number of hobbyists in non-reef aquariums, as well. However, while it may seem to be everywhere in the marine aquarium hobby, many people literally know next to nothing about it, and few know lots about it. So, I'll run through some information on the subject, and maybe you'll pick up something from it.

What Exactly Is Live Rock?

For the most part, live rock is nothing more than limestone that has been collected from reef areas where loose rock rubble can be picked up.

These pieces of limestone that have been removed from reef structures typically have some sorts of reef organisms living in and on them, hence the name live rock. It's all of the things that can be found living in and on such rocks that give them the name.

How Does Live Rock Form?

A wide variety of organisms in the marine realm use calcite and/or aragonite to form skeletal/structural material. Both of the minerals are composed of calcium carbonate, which organisms can produce by removing calcium from sea water and combining it with some carbon dioxide (of course it's much more complicated than that.) Organisms such as stony corals use this material to produce their skeletons, while clams and snails use it to build their shells. Numerous sorts of calcareous algae use it to strengthen their structures or to produce tough rinds on surfaces, and even a host of plankton use it to build miniscule containers for themselves.


So, in a simplisitic sense, stony corals build skeletons, which accumulate and form the basic structure of a reef with the help of these other biologic and non-biologic activities. The corals make large skeletons, which are frequently broken up by storms and such, and are also overgrown by new growth Thus, the net result is a reef structure made of a jumble of these pieces and calcium carbonate glue. This structure may also have a highly variable amount of pore/void space within it, which is also colonized by living reef organisms.

afterwards. Or, it can also be a piece of limestone that broke away from a much older geologic formationon the seafloor that has been subsequently colonized. Either way, it's limestone with stuff on it, and if you break a piece in half it can be quite obvious at times. Typically what you'll see is exactly what you'd expect given this information on how it forms: chunks of coral skeleton, bits and pieces of shells and such, and a lot of limestone glue holding it together.

Where Does Live Rock Come From?

Live rock is collected in a number of places, although the availability list has changed a good bit from time to time. Many years ago, almost all of it came from Florida waters and was relatively cheap. Live rock has also been coming from a few Pacific areas, but it was far less popular; the cost and the freight charges from so far away were substantially higher, making it less profitable for stores.


Then the collection of "wild" live rock in U.S. waters was banned by the government in January of 1997, and there was no alternative to the higher prices of the Pacific stuff. Live rock started coming from a wide variety of places, including some you've probably heard of, such as Fiji, Tonga, and Samoa, filling the gap in the market. Most of these areas are still shipping today, but the aquacultured live rock business in Florida got going, too. Now the aquacultured live rock produced in the Gulf of Mexico and the Florida Keys has made its way into the market with the Pacific rock, the result being a variety of live rock from a variety of areas to choose from, with the interesting thing being that they are all a little different.

What Kind of Stuff Is On Live Rock?

That's a big question! With collected rock, you may find basically nothing on it, or you may find some of just about everything, depending on where it was collected and what type of rock it is. In general you can expect a significanty variety of microorganisms to be populating any given peice of live rock. Most most live rock will also show at least some coverage by coralline algae, typically giving it a patchy purple, pink, and/or red appearance. But that's about it for a large part of what you'll see for sale.


Large rocks quarried in Florida and used in
aquaculture are often more dense than others, but it
is still easy to see that they are nothing but pieces of
corals, shells, and such, all melded together.

On the other end of the spectrum, top-quality aquacultured rock often has an impressive variety of life on it. The microorganisms are there of course, but there may also be a variety of macroalgae, sponges, tunicates, bryozoans, worms, clams, snails, crabs, hermit crabs, shrimps, barnacles, brittle stars, sea stars, urchins, anemones, and soft and stony corals, etc. - lots of stuff!


What Is The Best Type(s) of Live Rock?

That's a tough one because, as I said, there are a variety of types from a variety of places, and I can't really say one particularly type is perfect for all occasions. For example, "Tonga branch" live rock looks just like the name sounds. It is really just broken up pieces of staghorn coral that have died, been "worked on," and have been overgrown by coralline algae.

Aquacultured live rock typically has the most live stuff on it, but if you are bulding a stacked-up structure, much of it would be killed or would slowly die off after being covered up. Conversely, much of the other Pacific rock has very little life on it, but often comes in especially interesting shapes, and is relatively lightweight. 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.

What you do want to keep in mind when trying to choose is that none of it is cheap, and while you'll want to make your tank look the way you want, you will probably also want to use the least amount of live rock to do it. Most Pacific rock is relatively porous and lightweight and has lots of open shapes. Thus, you can use fewer pounds (it's sold by the pound) to take up more room in a tank. If stacked right, just a few big pieces can really take up a lot of room and look great. Conversely, Florida rock tends to be less porous and can be relatively heavy, so it would take more pounds to fill the same amount of space. But Florida rock typically has so much more life on it compared to Pacific rock that it may be worth the extra cost to you.

With that being said, I should also throw in a bit about base rock. Base rock is basically live rock with nothing on it, and it may even be sold dry.

Does it Require Any Special Care?

When live rock comes in, it can and almost always will go through a period of die off (of the critters, not the rock itself).

Some people used to "cure" rock first to avoid any such problems. This basically meant keeping it in a separate, unlit tank until everything on it that could die did and wasted away. But this often seemed to lead to the production of expensive base rock. So most people don't cure live rock unless it is in really bad shape. You'll just have to make a judgement call on what to do should you find yourself in such a situation, as it could be possible to add smelly rock to an aquarium and do water changes until the stinking stops in an effort to save whatever else may still be alive on it. Going over each piece and hand-removing anything dead or dying before hand will be essential, of course.



Are There Things to Watch Out For?

As a word of precation, I'd be wary of buying a large quantity of live rock at one time from a mail order/online supplier unless they are very reputable (some are, many aren't). Instead, you may want to buy a "sample" shipment to check out, then order more. Because shipments can be delayed or subjected to detrimental temperature extremes, if you are buying a lot you may want to get a few separate shipments anyway. That way if anything goes wrong it may only get some of your rock and not all of it. Of course, this really depends on your own situation and needs, and doesn't apply to purchases made at local shops.

And one last note: Whether you are buying at a shop or somewhere else, don't buy all small pieces! Buy big pieces, as they are far easier to arrange in ways that take up the most amount of space per pound used. If you buy 100 potato-sized pieces, you'll likely end up with a pile of live rock in your aquarium that resembles a pile of 100 potatoes.

More to follow.....