What is live rock? And do you need it?

Live rock…what is it? and do you need it in your aquarium? In this article we are going to explore the reasons why you should and should not have live rock in your tank.

What is live rock?

Despite it’s name, live rock is actually not a rock that is alive and is a living organism. It is actually a hard substance that was once made up of corals, coral reefs and calcareous organisms. However, the ‘live’ component of the live rock name most likely comes from the function that it serves in your tank.

Due to the components in the live rock and it’s porous surface, the live rock is a perfect surface area to house the ‘live’ bacteria in your tank that will facilitate the nitrogen cycle and help to remove the toxic substances that can result from leftover food and waste from the fish.

What are the different types of live rock?

Live rock is readily available in your local fish store (LFS), and it can come in different forms.

Wet Live Rock


source: saltwateraquariumblog.com

You will recognize this type of live rock at your LFS because they will have it in a tank with a filter system running the water to circulate the water through the rock. Live rock is particularly handy because in theory there should be live bacteria on the surface of the rock. This is perfect for a new tank set up as it will expedite the cycling process and have your tank running quicker.

However, purchasing wet live rock with the live bacteria can come with certain risks. You also don’t know what other ‘live’ things are coming along for the ride with the wet live rock.

Dry Live Rock


source: kanbkam.com

If you don’t want to risk introducing anything unexpected to your tank, you can always opt for Dry Live Rock. This is live rock that has been dried out. As you can appreciate with no live bacteria on the rock, the live rock will take longer to develop in your cycling of your tank.

The main advantage of dry live rock is that you won’t be introducing any nasty surprises into your system and you can let existing bacteria settle and multiply on the rock.

What are the benefits of having live rock?

Probably the main reason why reefers are so keen on live rock in their tank is the filtration benefits that it provides.

Earlier we talked about how the Live Rock houses the live bacteria in your tank to facilitate the nitrogen cycle. Let’s look at how this occurs.

Any uneaten food and waste expelled from the living fish and corals in you system, if left unattended to, will decompose into toxic ammonia. If the levels of ammonia increase too high, it will become a toxic environment and will likely make your fish and corals sick, and eventually die.

To deal with this excess food and waste you will need a clean up crew (hermit crabs, snails, worms, etc).

Once broken down, the uneaten food and waste turns into ammonia, nitrite and phosphate. It is at this point that the benefits of live rock kick in. The live rock will convert and filter the gases into less harmful gases, like nitrate.

Nitrate then gets assimilated by the algae and nitrifying bacteria living on the live rock and is effectively dispelled from the aquarium via gas bubbles through the surface of the water.

Check out this informative video about live rock from one of our favorite people at the BRStv team. 



Live rock should be one of the first things you consider when starting your new reef tank.

Live rock is an essential part of any reef system you are designing and developing. Not only does it look great in your tank. The natural compounds in the rock make it the perfect environment for the naturally occurring bacteria to thrive and help assist with the nitrogen cycle in your system.

If you have any questions about live rock or would like to find out more please leave a comment below and we will write back with an answer.

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