Live Rock – The Ultimate Guide

The role of Live Rock in an aquarium is a vital one. This guide helps to answer the many questions about what it is, why we need it, how to care for it, and how to select the best type for you.

What is Live Rock?

Live Rock is the broad taxonomic classification given to rock and reef structure which acts as a host to the many marine organisms that live on and within it. Live Rock is usually comprised of calcium carbonate but it can be made of many different materials including synthetic substances, concrete, and even the aragonite skeletons of ancient stony corals that have since passed on to the big aquarium in the sky. Live Rock is the foundation of our natural coral reefs in the oceans as well as for the aquariums and fish tanks in our homes.

Benefits and Purpose of Live Rock in your Aquarium

Live Rock serves many beneficial functions to the aquarium hobbyist, the most significant of which is its role as the biological filtration for your tank. Aquariums are closed systems, all food put into the aquarium for your fish and other inhabitants must also exit the aquarium somehow. Live Rock facilitates the means by which the food is broken down and exited out of the tank. Biological filtration is extremely important for the health and longevity of your aquarium inhabitants. You may ask how in the world does a rock do that, I’ve never seen them move, let alone clean my tank. The process of breaking down food from entry to exit takes several steps and is part of the nitrogen cycle that is always occurring inside your aquarium.

On first pass, the small filter feeders and cleanup crews such as emerald crabs, spaghetti worms and other invertebrates living on and within the Live Rock consume the uneaten food portions and fish waste. As the waste particles have now gotten smaller they will convert to ammonia, nitrite, and phosphate. Live Rock will actively facilitate the conversion of these toxic chemicals into less harmful products such as nitrate. Next, these nitrates can be quickly assimilated by the different algae and nitrifying bacteria (both aerobic and anaerobic) contained within the rocks. Finally, the majority of these nitrates will convert to nitrogen gas and will exit the tank via the gas exchange at the water’s surface. If you have more waste in your tank than your Live Rock can keep up with, you may need to do periodic water changes or acquire more Live Rock.

Live Rock is a far more efficient filter than any powered aquarium filter which can not contain any anaerobic bacteria for waste conversion as this type of bacteria only resides in oxygen-less spaces such as inside the Live Rock and within deep sand beds.

Introduction of Life and Diversity

Live Rock contains a diverse ecosystem of life and is often the only manner in which to introduce such a vast array of species into a closed system such as your aquarium. Coralline algae, beneficial bacteria, filter feeders, pods, corals, and other small invertebrates are all contained on and within each live rock, all contributing to the overall water quality of the aquarium. ARC Reef offers a version of Live Rock that has more life and critters than any other product on the market, check out our Premium Live Rock for Sale to read more about this option and how it can greatly increase the bio-diversity of our aquarium.

Habitat for Your Fish and Corals

Live Rock serves as a habitat and home to nearly all of the marine life in your tank. It provides protection, shade, food, and even acts as a nursery. Live Rock provides the base on which all your corals will grow, and plenty of holes for your frag plugs to fit nicely in. Without proper habitat in your tank, your fish will be more stressed and susceptible to disease. The main goal is to try to replicate what you would find in nature, and having an adequate amount of Live Rock helps to achieve this very important goal.

Coralline Algae and its Role on Live Rock

Coralline Algae is a red algae in the order Corallinales. It is an encrusting algae. There are over 1600 known species to date. The colors of these algae are most typically pink, varying shades of purple, and red, but can even be green, yellow, blue, and white. It is found in every ocean in the world and from inter-tidal zones that are exposed at low tide, all the way as deep as 1,000 ft. Coralline Algae is a slow and steady type grower, but its growth rate is approximately 10x’s more rapid in tropical waters than in the Arctic. At first glance, you may take note of the pretty colors, almost like an artist came along and left some abstract pink and purple brushstrokes all over the live rock. While Coralline Algae is a colorful component and adds to the overall aesthetics of your live rocks, it plays an essential part in reef health in a closed tank ecosystem.

It acts as the cement which binds the reef materials into a sturdy structure. It out-competes other nuisance algae like hair algae, green algae, diatoms, and matt algae in a normal reef environment with proper water chemistry. It looks attractive and gives coloring to your aquarium.

Coralline Algae will not appear in a tank or closed system on its own like other nuisance algae. It must be introduced into your aquarium, usually from purchased Live Rock or scrapings from a friends tank. High-quality Live Rock will have dozens of different species and colors of Coralline, all competing for space on the rock.

Live Rock Changing Colors

When you first place Live Rock into a new aquarium, the Coralline Algae may darken a bit due to the stress of being transported and the shock of new water chemistry. This usually lasts just a few days. You may also notice some white patches, this is all normal and the vibrant colors will return again. Coralline Algae will grow in all different lighting, temperature, and water .. With over 1600 different species, every species has it’s own preference though. So while your live rock comes with many different species on it, each species has its own preferred environment. Some species will like it bright and hot, while others will prefer the shady underside of a rock. They will eventually hash it out among each other on who will take what section of each rock, and sometimes a few species will want to try to claim it all. This negotiation process (and sometimes battle) for tank real estate leads to why your live rocks will change colors over time. If you are trying to seed a new tank, Coralline Algae will seed faster with higher flow, higher temps, and by scraping some of the rocks with a butter knife or flat head screwdriver. For more information on Coralline Algae visit our Guide to Coralline Algae.

There are many types of Live Rock available for the saltwater aquarium hobbyist some are wild collected and other types are farm raised or aqua-cultured. Below are a brief description of the most commonly found types.

The most common type available. Porous and lightweight. Fiji Live Rock varies vastly from one supplier to the next. Some re-sellers get it air shipped but the price usually skyrockets. Most Fiji rock is boat shipped and can spend up to 30 days in transit before arriving in Los Angeles International Airport. All Fiji rock requires curing.

Tonga Branch Live Rock:

Very dense which reduces the variety of life that can live within it. Interesting shapes and good for building vertically in the tank. Can make a nice addition to other rock but not recommended as the only type of Live Rock in the tank.

This is a fairly new type of live rock that comes from Fiji. It is porous and lightweight. It has nice shapes and is usually shipped in slightly larger pieces. It is shipped via boat and air. Air shipping is the only recommended method but even air freight takes over a week to clear customs and reach its final destination. All Live Rock originating from Fiji requires curing. Pukani Rock is well known for leaching phosphates back into the tank. Curing Pukani Live and Dry Rock can take over 6 months. Elevated PO4 levels can lead to battling nuisance algae like hair algae for as long as several years in time. Using lanthanum chloride may help shorten curing times but is not recommended as the rock has been reported to absorb the chemical and leach it back later in time.

Considered the most environmentally friendly option by far. Most countries including the United States, the Bahamas, the Marshall Islands, along with an ever-growing list of nations have banned the destructive practice of breaking apart coral reefs and exporting the reef as Live Rock. Aquacultured Live Rock is sourced from inside the earth, usually calcium carbonate and placed in the ocean to spawn new life on and within it. Aquacultured Live Rock varies in size, shape, and density with each individual farm. The most experienced producers will choose only the highest quality source rocks that are low in density, interestingly shaped, and very porous.

“Aquacultured Live Rock has several key advantages over all other types.”

It’s a sustainable practice that helps rebuild our natural coral reefs right here in the U.S. you are also equally helping coral reefs in other countries by not creating demand for a product that is produced from destroying their own reefs.

Ships from within the U.S. and requires very little curing or no curing at all.

Premium Aquacultured products can have the same weight, density, and shapes as wild harvested Live Rock. It is important to select the right producer.

The location where the seed rocks are placed also matters greatly on the final product. Live Rock that is harvested in the Gulf of Mexico is known as Gulf Live Rock. Gulf-rock will have more plant-based life such as macro-algae. Live Rock that is aquacultured in the Atlantic Ocean, known as Ocean Live Rock or Caribbean Live Rock will have more types of coral growth due to the lower levels of sediment and higher par levels. Both locations have their inherent risks and dangers from storms, wave action, and a shifting sand bed that can bury a farm’s entire crop overnight.

ARC Reef offers several different types of Live Rock and varying price points. Here are our most popular types:

ARC Reef Premium Live Rock for Sale – Several years of growth and packed with life. They have the highest yield of beneficial bacteria and coralline algae on them. They have a minimum of 2 years of growth and almost always contain corals, sponges, filter feeders, and some amazingly cool invertebrates as well. Our Premium Live Rock never disappoints.

ARC Reef Live Rock for Sale – An economical alternative to our premium version. They have between 1 and 2 years of growth on them. Contains over 60% coralline algae coverage.

ARC Reef Dry Rock for Sale – Aquarium base rock full of holes and crevices. Every rock is hand selected from our quarry to be porous and uniquely shaped.

Man-made or synthetic Live Rock is a new product category and has its full range of pros and cons. It is sustainable and environmentally friendly, the same as aquacultured Live Rock. Depending on the company and version, they can look fake and artificial. Man-made Live Rock will lack the diversity of life that is so desirable for your closed system tank. They may look bright and alive with different colors of coralline algae, but don’t be fooled. Artificial Live Rock will never contain all the beneficial organisms that make Live Rock Live. The paint or dye used to color the Live Rocks negatively impact the rocks by clogging the pores of the rock on a microscopic level. This will reduce the biological effectiveness of Live Rock. They are made from aggregates and paste. The aggregates are sand and gravel or crushed stone; the paste is water and portland cement.

Each manufacturer will have their own formula but they will all need to be cured before placing in your aquarium. This curing process is not for dead organics to be removed as in the case for real live rock, this curing process is for the leeching of hydrates. Freshly made Live Rock has high alkalinity with a pH reading of 12-14 which is even a higher pH than Clorox bleach. The PH level typically drops with the carbonation of the concrete. Some manufacturers of artificial Live Rock will cure these rocks before shipping, and it is absolutely vital to find this information out first before placing them in your fish tank.

Environmental Impacts of Live Rock Collection in the Wild

Unfortunately, not all live rock is beneficial to our marine ecosystems. Most commonly available live rock is harvested directly from living coral reefs in Fiji and other small island nations in the indo-pacific. Destructive practices such as using dynamite and crowbars to break up these rocks into smaller pieces have decimated reef systems all around the globe. Many nations including the United States and the Bahamas have banned this practice many years ago, but the U.S. is still the leading importer of wild harvested live rock.

Does all Live Rock need to be Cured?

Live Rock Curing is the removal of dead and decaying matter from on and within the rocks. If there is no dead or dying organic matter than your rocks do not need to be cured. You can test this in two ways. The first is the rather unscientific method. Hold your nose up near the rock and smell it. If it smells like the ocean or a jetty at low tide your good to go, if it smells strongly like rotten fish it will need to be cured. The more scientific approach is to place your new live rocks in a container of salt water for 12-24 hours, then test for ammonia. If the ammonia level is high your rocks will need to be cured. If the level is at 0 ppm or barely detectable than no curing is required. Typically all Live Rock from Fiji and the Indo-Pacific will need to be cured due to their long transport duration. Not much life can survive that long out of the water.

Aquacultured Live Rock that is harvested here in the U.S. usually does not need to be cured, as it was happy and alive in the ocean just several days before it lands on your front step. Temperature extremes will always be an influencing factor. If you’re having the blizzard of the century your Live Rock could get delayed or stressed out from being in a cold warehouse or truck for too long. So it’s always a good idea to be mindful of your current weather conditions when ordering Live Rock and pick a shipping method that you are comfortable with.

If your Live Rocks failed both the smell test and the ammonia test than they will need to be cured. If this is a brand new tank with no inhabitants in it yet, the rocks can be cured in your main display tank. If your tank is already established with fish and corals in it then you will need a separate tank. A Rubbermaid trash can or a children’s kiddie pool work just great and are fairly inexpensive. The larger the water volume the better.

Fill your container 3/4 with either fresh seawater or salt-mix and good RO/DI water. Reverse osmosis deionized water is always the purest option, as city water and well water may contain chlorine, chloramines, phosphates, as well as other unwanted minerals. Inspect your Live Rock for dead organic matter and sponges. If it’s black it almost always means that it’s dead and sponges rarely survive this process. Use a medium bristled brush to remove all the dead that you can, then rise them. Place your Live Rock in the tank and top off to bring the level near the top. You will want to attach a protein skimmer to remove waste, a powerhead for circulation, and a heater to keep the temperature above 80. The more flow and the higher the temperature (without going over 82), the faster the curing process will be. Test the water 2-3 times weekly for ammonia and nitrites, this will give you an indicator on how close they are to being done. Do a 100% water change any time the ammonia is over 5 ppm or it has been more than 5 days since your last water change. It is often said to do 2 100% water changes per week, but this is just a guide. If your ammonia is above 10 ppm, I would suggest more, if your levels are below 5 ppm than every 5 days is plenty. You can speed up the curing process by scrubbing the rocks with a soft-medium bristle brush immediately before doing each water change. Once your ammonia readings are at 0 ppm and your nitrates stop rising, the curing process is complete and you can transfer your fully cured live rock over to your aquarium. This process can take anywhere from 1 week to 3 months, with the exception of pukani dry rock and Fiji boat rock which can take more than 6 months to fully cure.

Important notes: Do not light your live rocks with full spectrum or full intensity lighting during the curing process as this may cause an algae bloom. Light them with either actinic lighting or natural lighting by having them in a room that gets ample indirect sunlight. If using actinic lighting, the photo-period should be no more then 4-5 hours per day. If you notice any sponges on your rocks, it is recommended to remove them, as they rarely survive. The curing process can be quite a smelly endeavor, you might want to give a little warning to your significant other, otherwise, you may be sleeping with your rocks for a few nights! It’s a good idea to keep carbon on hand, which will reduce the odor if needed. Remember not all Live Rock needs to be cured, if you purchased aquacultured Live Rock harvested in the U.S. you can skip this entire process 90% of the time. It pays to do your research first, and avoid the hassle of curing entirely. For more information on curing, visit our Live Rock Curing Guide.

Live Rock Hitchhikers

There is a negative stigma attached to the words Live Rock Hitchhikers, but the majority of all the hitchhikers that will come on live rock will be good and with only very few exceptions are there some bad or questionable hitchhikers. Lets first dive into the good ones. There is no better method of increasing the biodiversity and life of any aquarium than to introduce Live Rock into your closed system. The organisms living on and within these rocks are a natural sampling of what is found on the coral reefs and all play some small role in the overall quality of your system. Some of the many beneficial hitchhikers include filter feeders, worms, starfish, invertebrates and even corals will hitchhike in on your new Live Rock. In general, it is wise to “dip” your coral frags before placing them into your tank, but the same cannot be said with regards to your Live Rock. The old school of thought is that all hitchhikers were bad, but hobbyists have come to realize that there is a great benefit to nearly all the extras that come with live rock and the hobby has now shifted its focus on trying to replicate the diversity that one would find on a coral reef in the wild. Just as we once thought that all sharks were bad, we have finally realized that every creature is needed in proper proportions in order for an ecosystem as a whole to succeed.

Hitchhiker Removal Techniques

The Hyper-Salinity and Hypo-salinity Bath – Some websites state that you can submerge your new Live Rock in a bucket filled with salt water with a specific gravity of 1.035 to 1.040 or into freshwater for one minute. After a minute, hitchhikers including mantis shrimp, bristle worms, and gorilla crabs will quickly have retreated out of the rock and will be in the bottom of the bucket. While this does work to a degree, your doing way more harm than good here. First, you’re stressing out all life on the rock, including good bacteria, coralline algae, and all the good worms and inverts. You also may start the tank to cycle again from all the die off as a result of this method. This method is much like blowing up a building to catch a mouse that lives there. Be very wary of anyone or any company that is dishing out this advice.

Bait Traps – In our experience if there is something really driving you crazy the best method of removal is targeted removal, not a blanket removal chemical that stresses or kills everything. Bristleworm traps and a larger trap called Ultralife X-Terminator sell for just over $10 on Amazon and work wonders.

Introduction of a natural Predator – You can also go the natural method and introduce that pests natural predator into your tank. Both a Melanurus Wrasse and 6-Line Wrasse will basically eat any pests that they come across.

Portion Control – If you have an uncontrollable pest situation, step one should be to analyze what’s going on and how did this come to be. In the wild, there is always balance. You should always strive to create equilibrium in your saltwater aquarium. Many times the culprit of how something got out of control in your tank is due to overfeeding or poor husbandry. If you want to reduce the population of any particular species, simply reduce their source of growth.

Atlantic Reef Conservation (ARC Reef) is a state and federally licensed Aquaculture Facility looking to bring about positive change to our coral reefs. For every 1 lb of Live Rock purchased we deposit 10 lbs of new reef material into the ocean. To date, we have created over 43,500 sq ft. of new coral reefs.

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