Your marine aquarium and live rock

Live rock- the type that you use in a marine aquarium, not the kind you hear at a concert- is one of the foundations of the natural and healthy saltwater marine aquarium, and while it is possible to set up a tank without it, it is not recommended! For the first time would-be marine fish keeper, hearing the phrase “live rock” bandied about can be confusing, and not everyone knows with any confidence what the term actually means!

If you are in the ranks of the confused beginner and want to learn more about what live rock is, what it does and why it is important, read on, because in this article we will discuss live rock and its purpose in the aquarium in more detail.

What is live rock?

First of all, it is important to point out that live rock is not actually alive in the sentient sense in and of itself; while many of us owned a pet rock as kids, this is not its larger, aquatic brother! Live rock is composed of natural rock that is either taken from coral reefs physically (a practice that is not recommended, due to the degradation this causes to the natural reef environment) or coral, reel and inshore rock that is gathered from the ocean floor once it has broken off naturally.

The rock is considered to be “alive” thanks to the huge range of both microscopic and macroscopic marine life that dwells within it, including but not limited to sponges, coralline algae, macro algae, worms, shrimps, and other small organisms.

When is live rock actually live?

This is the clincher that you need to establish before you buy your live rock, as reef rock that is not live will serve no purpose or benefit to your tank, other than as decoration! When you are buying or choosing your rock, consider the following points:

• Rock is not live if is dry and has been left out of water, nor if it has been kept in freshwater.
• If you put dried (dead) reef rock into an aquarium that already contains live rock, the new rock will eventually seed from the old rock, and become live; but this process takes time.
• Depending on how long your live rock is in shipping or how long it takes you to get it home, it may begin to die off before you place it in your tank, meaning that it may need to be cycled before adding to the tank.
• If you can see that the rock is live by means of identifying living organisms on and in it, then it is obviously alive; however, don’t assume that it is dead just because nothing has revealed itself on the surface yet!
• Dense, base rock from the middle of a reef can also be used in your displays, to support and hold the live rock on the outside. However, dense base rock does not seed and become live, and should be significantly cheaper to buy accordingly.

Live sand

Live sand, like live rock, is seabed sand that is specially selected for its colour and appearance for use in the home marine aquarium. Like live rock, live sand contains micro organisms and bacteria that is beneficial to the tank.

Live sand is usually bought pre-packed in sealed bags, which are wet with sea water and can keep on the shelf for a relatively long time before purchase without dying off.

Why are live rocks and live sand beneficial to the marine tank?

Live rock and live sand when correctly added and cycled in the tank will serve as the main natural source of filtration in the tank, as well as improving the appearance of the tank, lending a natural look to it, and providing shelter and a source of food for some of the tank’s inhabitants.

When you add live rock and live sand to the tank, you also introduce a wide range of bacteria, algae and small invertebrates too, which all serve to improve the quality of the tank water and maintain its natural levels. It is much easier to keep a tank that contains live rock stable and within safe parameters than it is a tank with only mechanical filtration.

Live rock, being porous, offers a huge surface area in total for the tank’s water to filter through, and a wide range of elements in the tank get processed through the rock along with the water. Nitrate, ammonia and phosphates become filtered and processed by the algae and corals on the rock, which can then be absorbed by them, or denitrified by bacteria to add to the growth of the rock colony.

You will still need to run a range of other tank filtration systems along with your live rock, such as a protein skimmer, sump, mechanical filtration and seeded biological filtration trap, but with live rock and sand in the tank too, all of these things become easier to manage.