[Maryrosi]

Another interesting and informative article
by Mike Paletta

Base rock generally refers to large bulky pieces of live rock that have either been buried under sand or under other pieces of live rock. This rock usually is less porous and does not contain a lot of external life or coralline algae. This rock may also contain significant sand or silt in its spaces. Consequently, it needs to be rinsed thoroughly before beginning the curing process. This rock is, like its name implies, a good rock to use as a base for setting more decorative rock upon. Using this rock for the bottom of the mini-reef structure is much better than using terrestrial rock. When terrestrial rock is used, it not only increases the risk of introducing toxic compounds to the tank that are not present in live rock but it also does not provide the surface area necessary for proper biological filtration. Terrestrial rock such as lava rock or feather rock, which is volcanic in origin, also seems to act as a magnet for detritus accumulation due to their very-porous structure. As a result, micro-algae blooms are frequently a problem on these rocks and may be a constant challenge to keep under control. These types of rock are often used as a means of cost savings, but over time their need for constant cleaning and other problems makes them a more expensive alternative.

Turf rock is the complete opposite of base rock in that if anything, it contains too much life. This rock is taken from the turf zone where many of the macro-algaes thrive. This rock usually contains coralline algae as well as these macro-algaes. For best results, I usually pull off this macroalgae as discussed above. This rock may also contain large populations of bristle worms, so care should be taken when handling it. When cleaning this rock, care should be taken not to get jabbed by one of these pests when picking it up. Also, due to this rock being exposed to air for a long period of time during shipping, there is usually a large die off of bristle worms and other worms so measures should be taken to allow for the easy removal of these worms from the bottom of the tank once they die. Tweezers are a handy way to remove these and any other pests that may be encountered during the initial cleaning process.

Worm rock differs from the other two types in that this rock usually contains a preponderance of hard tubeworms directly in the rock. These are usually quite decorative. The only problem is that this type of rock usually comes from water where there is a high amount of suspended matter and high nutrients. As a result, these animals need to be fed to remain healthy. If too much of this rock is used, a risk of polluting the tank develops if these animals are fed enough to remain healthy. Conversely, if these animals are not fed adequate amounts of food, they may die and pollute the tank as a result.

The best type of rock to use is what's referred to as reef rock, rubble rock or just plain old live rock from a good location. Some of the best locations for live rock include: Fiji, Tonga, Nambu and Indonesia. This type of rock consists of the pieces of old coral skeletons that have broken off and fallen close to the reef in relatively shallow water. As a result, it contains the best growth of coralline algae as well as small colonies of other animal and plant life. Depending upon where this rock was collected, it can contain colonies of coral as well as tunicates, bryozoans, zooanthids, sponges, and sea squirts. This type of rock should make up the bulk of the mini-reef structure.

Not only does the zone from where the rock was taken impact its characteristics but so does the body of water. Live rock from the Caribbean, Atlantic, or Gulf rock is usually very densely structured due to it having come from corals with very dense skeletons. This rock, for lack of a better term, resembles bricks. Live rock harvested from the Pacific Ocean is usually far less dense than its Atlantic counterparts. This rock usually contains more branching structures. It also contains more nooks and crannies and will weigh less than Atlantic rock when the same size pieces are compared. This type of rock is currently being collected from Fiji, Tonga, Indonesia, Nambu and the Marshall Islands. This rock is usually slightly more expensive than its Atlantic counterparts due to the increased expense of shipping. However, due to its less-dense nature, less of it is required to fill a given space than Atlantic rock. This open structure and myriad collection of creatures that arrive on Pacific reef rock make this rock my choice for configuring a reef. The rock also differs markedly in terms of its characteristics depending upon from where it has been taken from. Live rock from Fiji is currently the industry standard. This rock is very open and can be purchased in pieces up to 35-40 lbs in size; which are quite useful when decorating large tanks. This rock has been extensively harvested and as a result it can vary markedly in terms of its quality. Some rock can be full of life, while other pieces within the same box can be completely devoid of life. All of the rock is just as valuable over time, so even if it looks stark when introduced, this should not be a deterrent to its use.

Unlike Fiji rock, Tonga rock is more branched in nature and looks like thick twigs or sticks. Using this rock for the basis of a mini reef produces a very open structure. Initially, it may be difficult to balance the corals upon this structure, especially if Tonga rock is used exclusively. If some of this rock is used with other types of live rock, it can help to keep the overall structure open.

Live rock from Nambu usually resembles that from Fiji, but with slightly less coralline cover. This rock often arrives with small coral colonies still attached. These colonies should be removed and placed in a tank with clean water and good filtration as the curing process for the fresh rock will usually kill off the coral colonies.

Please note that even rock from these locales differ in terms of its quality. The level of quality is dependent on how the rock was handled after harvesting and during shipping; so, much of the quality control is out of the hands of the importer. The level of quality can be adversely affected if the rock sits in the boat or on the dock for any length of time out in the hot sun; virtually everything on it will perish. Much of the life on it will also be killed during shipping if it sits on a hot or freezing tarmac, since it has little water around it for insulation.

As mentioned above, even during the curing process the rock should be placed in the position close to what its final position will be in the reef tank. The positioning of the rock is crucial for several reasons. The animals present on the rock should be positioned close to how they were positioned in the wild. If the corals, invertebrates or coralline algae were positioned upwards or sideways to capture strong light or strong water movement, that is how they should be positioned in the tank. The rock's natural orientation needs to be taken into account so that things that were growing in one direction in the wild will continue to do so. The mini-reef structure needs to be stable so that as corals and other invertebrates are placed on this "platform". It is important to make sure that they do not rest precariously or fall. The mini-reef structure also needs to be as open as possible to provide lots of hiding places for the tank's inhabitants and to look natural. A reef does not look like a wall, but like an open rock lattice. More importantly, this open structure should allow water to readily move around and through the entire structure so that detritus does not settle and accumulate in any one spot. Lastly, the rock should be arranged so that it is aesthetically pleasing and mimics, at least in part to, what a small portion of an actual reef looks like.

When starting a reef tank, it is not necessary to pile the rock all the way to the surface. Rather than looking at rock by weight, it is more realistic to consider its volume. Rather than looking at weight as being the determining amount of rock needed, it is much more useful to add rock until one-half to two-thirds of the tank is full. More than this amount is not necessary as the corals will very quickly fill the space that is left open.

Most mini-reefs are built to resemble a wall with the rock stacked upon each other like bricks. While this may provide the most stable structure it does not resemble a reef, which is in essence what we are trying to capture. This wall design is often the result of the tall thin tanks that are most commonly offered for sale. Fortunately, lower and wider tanks have become more readily available, as have custom tanks. Because of this, it is now much easier to design a more realistic and interesting reef tank. A mini-reef structure that contains arches, long overhangs, deep caves and interesting ridges and ledges using good live rock is how a reef tank, and any saltwater system for that matter, should be designed. By selecting good quality live rock and properly placing the rock in an interesting manner, it is possible to provide not only good biological filtration, but also to provide a tank that is pleasing to look at. Live rock is crucial to a reef tank. Understanding the differences in the different types of live rock, as well as how to cure it properly goes a long way in ensuring the success of a reef tank.