A Comparison of Live Rock and Aquarium Aquascaping to MarinePure® Bio-Filter Media

April 13, 2020 Phil Overton

Picture an asymmetrical ocean rock encrusted with coralline algae. Attached to the bottom, accentuating the purple of the algae, are several flamboyant purple mushroom corals. Nearby, swimming peacefully, is a tiny colorful royal gramma that can easily blend into the background of the algae and the corals. Inside the rock, invisible to the eye, are even more living marine organisms all sharing this rock and making it their home.

This rock is what hobbyists call “live rock”. For years, it has been the most popular choice for aquarium biological filtration—and for a good reason. Using live rock has many advantages. In this article, we’re going to talk about what these advantages are, in addition to some of the drawbacks of using live rock. We will also discuss other methods for decorative aquascaping, and then we will compare these methods to using MarinePure® Bio-filter Media so you can better understand which one might be the right one for your tank. 

What is Live Rock?

Live rock is a naturally occurring ocean rock, composed of the aragonite skeletons of dead corals in addition to other hard or calcareous organisms. It is obtained by either taking it directly from the ocean or mined from now dry seabeds and cultured in a local fish store (dry rock). The rock itself is not alive, as the name might imply, but the organisms that inhabit it are, which is how the name originated. 

Starting a tank with live rock is highly valued because it immediately introduces numerous beneficial bacteria, algae and organisms that contribute to the overall aquarium water quality. Because they already host aerobic and anaerobic bacteria, the time to cycle your tank can be greatly reduced—in some cases to a matter of days. 

Live rock can host a wide range of marine life commonly referred to as “hitchhikers.” These hitchhikers can include snails, copepods, algae and corals, all of which will help increase the biodiversity in your aquarium by matching more closely how these lifeforms balance in nature. Additionally, many of these organisms will help you filter your tank’s water, keep nuisance algae at bay, help process waste, and also oxygenate your sand-bed. 

Keep in mind that not all hitchhikers in your live rock are good for your aquarium. Hiding in your rock could be Aiptasia anemones, which can overpopulate your tank; mantis shrimps whose highly developed claws, or clubs, are strong enough to smash through your aquarium glass; and bubble algae, which can encroach on and envelope your corals causing them to die. 

Copepod (Zooplankton) are a group of small crustaceans found in the marine and freshwater habitat.

An additional benefit of using live rock is that it contains leachable calcium from the calcified skeleton of dead corals; this means it can act as a buffer and help stabilize the water chemistry in your aquarium and maintain a stable pH. 

Live Rock as a Bio-Filter

When contemplating whether to use live rock or another bio-filtration method for your aquarium, one vital thing to consider is the porosity. Porosity is essential for beneficial bacteria: the higher the porosity, the more access to the interior of the rock, and thus the more surface area will be available for beneficial bacteria to grow and control the nitrogen cycle. Ultimately, it’s the available surface area that determines the nitrogen load the system can handle. However, the porosity of live rock can be inconsistent and depends on many factors including the type and the origin of the rock. Additionally, the porosity of live rock includes many dead-end channels. This is not ideal given that if the channel opening gets blocked with algae or biofilm, then the entire interior of the channel becomes inaccessible for beneficial bacteria. 

Live rock can also be heavy and take up a lot of space, making setting up and cleaning the tank difficult. At the recommended levels of one to two pounds of live rock per gallon of water, the weight and volume will add up to quite a heavy tank/sump. Not to mention there will be a significant amount of water displacement, meaning the tank will have less water which can lessen the stability of the system. 

Furthermore, adding live rock to an existing aquarium can lead to a spike in ammonia. Organisms might not have survived the transport and water changes which causes die-off. Also, the longer the live rock has been exposed to air, the more die-off you will have. All these drawbacks are nothing compared to the number one concern. Overharvesting live rock from the ocean’s reef, and the effects of global warming, have become a problem in some areas of the world, creating a huge threat to the long-term survival of our natural reefs. Although many governments and international organizations have been taking steps to address this concern, we are still struggling to keep our coral reefs alive (1) (2).

A saltwater set up with live rock as your only biological filtration method is often costly. Using mined dry rock instead, that is then inoculated with beneficial bacteria, can reduce the overall cost. 

MarinePure® as a Bio-Filter

MarinePure’s Open Porosity

MarinePure® is a product that can either supplement or replace your live rock or other aquascaping. It is a ceramic specifically designed to house beneficial bacteria that will target ammonia, nitrite, and nitrate. MarinePure® has a unique combination of vast surface area and up to 90% open porosity. This combination allows for water to easily flow through the media and not around it, allowing beneficial bacteria to grow and make the most out of its surface area, thus providing bacteria with easy access to nutrients. This is known as MarinePure’s “Thin Bio-Film Technology™” The interconnected pores prevent the media from clogging, and even if a few random pores do get closed, there are many pores nearby that will still allow water into the interior volume. 

Since MarinePure® bio-filter media is a man-made ceramic, it does not come with any pests that can hurt your marine aquarium. However, there are many aquatic creatures that you do want to welcome in your aquarium and MarinePure® makes a great home for such welcomed guests. For example, copepods love to live in MarinePure® due to its large internal pore structure. Coralline algae will easily grow on MarinePure® and it makes an excellent base on which to attach and grow corals. 

MarinePure by Cermedia’s Product Family

Furthermore, the amount of MarinePure® bio-filter media needed to provide biological filtration to your water is significantly less than compared to live rock. For example, you only need one MarinePure® Block per 100 gallons of water to help with nitrate control. Compared to buying 100 pounds of live rock, this is a huge decrease both in cost and media volume with significantly less water displacement and weight. 

Unlike live rock, MarinePure® bio-filter media does not come with an already established beneficial bacteria colony. Therefore, you will have to patiently cycle your tank as you would normally do with any other bio-media. It also does not add calcium into your tank as a live rock would do, therefore MarinePure® will not be a pH buffer. 

MarinePure® bio-filter media comes in a variety of shapes and sizes making it easy to place in any location and in any tank size. Even in a compact space in your sump or inconspicuously in your tank. 

Other methods for Aquascaping


MarinePure Gems

Every aquarists has an idea of what they want their aquarium to look like. In saltwater it ranges from a minimalist tank with fish only, to a fully aquascaped tank brimming with corals and live rock. In a freshwater tank, the aquascape can be a planted tank or a complicated natural rock set up, to a small kid’s tank complete with plastic plants and a bubbling ornament.

In freshwater systems, the biological filtration is usually part of the filter, whether it is hang on the back filters or canister filters. Specialized media in the filter give additional surface area for bacteria. This allows the hobbyists to build the aquascape without needing to be concerned about adding surface area for beneficial bacteria. MarinePure® bio-filter media can replace the media in these filters to significantly increase the available surface area, and more importantly their biological capacity. 

There are also some beautiful man-made ceramic rocks specifically designed for their artistic appearance in a saltwater aquarium, such as the products from AquaRoche. With these products the hobbyists can focus on the appearance of the tank using their desired aquascape and allow MarinePure® bio-filter media to provide the bio-filtration out of sight in the sump. Not only will these products help you have a beautiful tank, but they will help you save the reefs by reducing the amount of live rock you would originally buy, keeping them where they’re needed the most, in our oceans. 

AquaRoche reef rocks with MarinePure bio-filter: hidden in sump

Which is better for your aquarium, Live Rock or MarinePure®?

In conclusion, MarinePure® bio-filter media is very similar to live rock but with even more surface area and porosity. It allows for a healthy population of beneficial bacteria to live in the media, helping to eliminate ammonia and nitrites and significantly reduce nitrates. It provides an excellent base for corals to grow on, coralline algae will easily grow on it as well, and it will also provide a home for healthy critters. 

Using MarinePure® allows you to select your live rock, dry rock, or other aquascaping materials and decorations based on the desired artistic appearance without worrying if there is enough surface area available to handle the nitrogen cycle. 

If you have any questions about which is the best option for your aquarium, please feel free to contact us and we will be happy to help you through the selection process. cermedia.com/marinepure

[1] https://www.earth.com/news/coral-reefs-sea-level-rise/

[2] https://www.nationalgeographic.com/environment/2019/04/great-barrier-reef-coral-not-recovering-climate-change/#close


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