MarinePure Biofilter Media

February 9, 2023 Cermedia

What is MarinePure®?

MarinePure, in essence, is a structured home in which beneficial bacteria can live and thrive. In an aquarium, ammonia, nitrite, and nitrate are naturally produced as a result of aquatic animal metabolism and dead plant matter breakdown. These molecules are harmful to the life in your aquarium. Beneficial bacteria convert these molecules to less harmful species. MarinePure, which is a man-made, fired, alumino-silicate ceramic, provides a uniquely efficient and protective space for these bacteria.



Years ago, a very knowledgeable scientist, developed a unique ceramic processing method that makes a porous ceramic. His original intent was to use it as a molten metal filter. That application never took hold, but luckily for us, he was also an aquarium hobbyist. He saw the possibilities that this new product could bring to improve bio-filtration in the hobby.

Bio-Filter media at the time was either a natural product (i.e., lava rock, live rock) which has an inconsistent density with closed or dead-end pores, Plastic (i.e., bio-balls) which have very little capacity and does nothing to remove nitrates, or manufactured (i.e., ceramic rings) which again, have dead-end pores and are inefficient. (Why do you need to put a hole down the middle of it? – discussed later). Thus, the ceramic, known as MarinePure, was born. In 2009 Cermedia LLC took up the MarinePure process and brought it to the wider world. Explaining the importance of efficient biofiltration and the uniqueness of Marinepure, we changed how hobbyists think about biofilter media, paying much closer attention to an often unnecessarily frustrating part of their aquarium keeping.


Unique Combination.

It is so simple…. but rarely achieved. There are two things that make a really good filter media….

1) Huge amounts of surface area. Beneficial bacteria create a biofilm to live in. Biofilms are “2D”, meaning they need space to spread out. If the proper nutrients are available, the bacteria will grow and multiply. The biofilm and bacteria live on most surface areas in the tank including all the equipment, glass walls, sand, gravel, and rocks, but it usually needs more area than is provided with those items. Too little surface area in a tank, and the biofilm competes for space and piles on top of itself, starving the underlying bacteria of its resources and dies. Now there are not enough healthy bacteria to handle the nitrogen load. On the other hand, with too much surface area…. Well, you cannot really have too much……. The bacteria will only grow if there is food available, and it has the space if needed.

2) Accessibility and pore size. Not only does the bacteria need room to grow, but the nutrient-rich water also needs to be able to get to the bacteria easily and the bacteria needs to be able to fit into the spaces available.

Picture trying to park a truck into a garden shed. It won’t fit. The space is too small, and all its surface area does you no good. It doesn’t matter how many garden sheds you have; it is all worthless. Now picture a long garage that holds 100 trucks in its length. A truck, in a hurry, parks at the entrance to the garage, now the rest of the garage is not accessible for other trucks. So, similarly, for bacteria, the size and shape of the porosity is important. First, the bacteria must be able to fit. Second, the pores need to be large enough and/or inter-connected so that pores can’t be blocked.

Therefore, combining the two important traits is key, your high surface area needs to be accessible. Some natural products have incredibly high surface areas, but the bacteria are too big to fit. Even if the bacteria does fit, the pores are dead-ended making them easily blocked. The interior surface area becomes unusable. On the other hand, on plastic media, all the surface area is accessible, but there is so little of it that there is probably more bacteria living on the tank’s gravel, décor, walls, tubes, and hoses, than on the media itself, where it belongs.

Having interconnecting pores also helps. If one way into the pore is plugged, there are many other ways to get inside. Picture our long garage example again. The garage now also has a backdoor, plus dozens of side doors, marking it virtually impossible to be blocked. This is how MarinePure is structured. There is always space for the water to move around and for the biofilm and bacteria to spread. In MarinePure, the pore sizes range from huge, to allow free movement of water and nutrients, to medium-sized pores, allowing for large amounts of bacteria and biofilm. MarinePure also has small pores. Small pores are the places where anaerobic bacteria like to hide out in bio-filter media.

Now, about anaerobic bacteria. This is where MarinePure really starts to stand apart. As the water goes past the beneficial bacteria, ammonia (NH4) is converted to nitrite (NO2). To do this, oxygen is pulled from the water and attached to the ammonia molecule. Another beneficial bacteria now acts, pulling in more oxygen to convert NO2 to Nitrate (NO3). Through this, the water becomes low in oxygen, and this is where anaerobic bacteria does its thing. Anaerobic bacteria still need oxygen, but since it is not available in the water, they strip the oxygen off the NO3 molecule and convert the molecule to nitrogen gas (N2). This gas can easily evolve out of the tank…. The nitrogen cycle is completed!


Summary, What MarinePure does.

A quick summary of the article so far, MarinePure biofilter media is a man-made ceramic with a huge amount of surface area for beneficial bacteria growth AND a unique porosity system, which we call OPEN-FLOW Porosity. It allows for the movement of water through the media via its large pores and delivers the water with the nitrogen molecules to the small pores, which have the high surface area and lots of biofilm. MarinePure is a compact and efficient way to control the entire nitrogen cycle in your aquarium, including converting nitrates to nitrogen gas. To learn more, this article gives a more detailed description of the nitrogen cycle.


Compare with other medias.

  • Plastics, i.e., bioballs – There are two problems with plastic media. First, they have extremely limited amounts of surface area. In a lab study we performed in 2012, showed plastic media performs just as well as a system that did not have media at all. There was biofilm growth everywhere in these systems, on the tank hoses, the tank walls, etc. The bioballs contributed no significant surface area to the system. As the new film grows, it chokes out the old film. There is a limit to the ammonia conversion capacity in the system.

The second issue with plastic media is there is no opportunity for low-oxygen zones to develop within the media. All the bacteria are exposed to oxygen. Therefore, the nitrates continue to rise and never get converted to nitrogen gas. The most common way to lower nitrates in this system is through time-consuming and expensive water changes. This is why the term Nitrate factory gets used with plastic media. They make nitrates, as designed. Check out this blog discussing this issue in more detail.


  • Live Rock (in Marine Environments) and other porous natural rocks. Natural rocks and corals can work well as filtration media in your system. They have significantly more surface area than plastic. However, there can be several drawbacks. First is consistency, how porous is the media? Does it have open porosity that connects to the outside?  Is it real tight so it plugs easily? Read this blog on how Live Rock compares to MarinePure

    Lava Rock

    There is a natural stone media on the market with an astoundingly huge amount of surface area. Even their own data shows that less than 25% of the surface area is useable because the pores are too small for bacteria to fit in. Not surprisingly, the media plugs easily. There was another ceramic media in Europe that published that “it’s so light (due to high porosity) that it floats”. Well, guess what, the pores are closed, if the water cannot get into the pore to displace the air, neither can the beneficial bacteria.


  •  Other ceramic media. There have been ceramic media around for a long time. They were usually an add-on to the more expensive filter, with unreliable data to back up their capacities. With the growth of MarinePure, ceramic media has improved as suppliers realized hobbyists want to see results. Manufacturers are now coming out with different products. A couple of notes about these newer media. They are typically made by pressing beads of ceramic or glass together and firing them. The problem with this method is that the surface area of the beads does not actually add up to much. Note in the graph below, there is an exponential increase in calculated surface area with decreasing bead or particle size.


If they used beads or particles small enough to get significant surface area, then the pores would be too small to allow the free spreading of the water and biofilm. They often plug up easily. In fact, some manufacturers of this media recommend you change it every 3 months!…. Throwing your beneficial bacteria away, just when it is getting good. (Note: There are Blocks of MarinePure’s predecessor still in use after 20 years and still going strong.)  Another note on these media. These often have a hole down the middle. Why?  To make them perform better. Really?  They need to remove media to make it perform better!  This is because the pores are so tight, the interior of the part would never get used, so by removing the interior, they are exposing some of the internal structure to the water. With MarinePure biofilter media, the entire part gets used, inside and out, the thicker the better.

There are newer ceramic media out now that do the opposite. They use larger beads pressed together to get their shapes, the actual surface area in this media is very small, but they do get good water flow. They look nice and are very strong, but when you handle them, they are very heavy. Where you want pores and biofilm, they have ceramic. It’s a “coincidence” that their published numbers are usually close or sometimes even match Cermedia’s scientifically derived results for MarinePure. It does not pass the logic test. We don’t suggest these media do not work, just probably at less than 10% of the performance rates that they suggest. But their boxes do look nice.


MarinePure Issues;

MarinePure is Brittle. If you ever handled MarinePure you notice the product abrades very easily. This is a function of the structure of the product. If you look closely at the walls of MarinePure’s pores, you will see smaller pores. Look even closer, the walls of these pores have even more pores. So, the actual wall thicknesses are very tiny. While MarinePure is made from a strong ceramic, the presence of these tiny pores makes the walls weak, and easily susceptible to damage. We recommend 1) handling MarinePure as little as possible, or 2) putting it in a protective enclosure, so it is not handled directly. A plastic mesh basket works well or try our New MarinePure VAULT which holds a gallon of MarinePure SPHEREs or 1 MarinePure BLOCK.

Is MarinePure a Nitrate Factory?  We hope so (sort of), it means it is getting rid of all the ammonia and nitrites, which automatically produces nitrates. But MarinePure takes the next step which solves that problem since it is a nitrate eliminator. The internal pore structure also means there are anaerobic zones that will also help control Nitrates. If you ever pull MarinePure out of your tank and sample the water coming out of the media, it will probably be higher in nitrates. These are nitrate molecules that were converted from ammonia and have not yet had the chance to be acted on by the anaerobic bacteria. They would be if the media was not disturbed. If, when you pull the media out the added nitrates are a concern, we recommend first putting the media in a closed container, bag, or bucket (while still submerged) and then pulling it out. These nitrates will now come out with the media instead of pouring back into the tank. Again, this blog talks about nitrate factory and plastic media, and why MarinePure goes the next step.

MarinePure adds aluminum to the tank. MarinePure, like many ceramics, is an alumino-silicate, which is the oxide form of aluminum and silicon. It has been kiln fired, making it inert, and is very similar in chemistry to a porcelain coffee cup. The current reef chemistry testing methods report all elements as ionic forms, regardless of which molecular form they are actually in. Any MarinePure particles will be reported as aluminum ions even if they are in the bound and harmless aluminum oxide form. There are also many other sources of aluminum in an aquarium that should be looked into (i.e. food) if you are having an aluminum problem. See our aluminum information blog for more information.


How to use. 

MarinePure biofilter media can be used almost anywhere in the system. In the tank? Yes. In the sump? Yes. In a hang on back filter? Canister filter? Refugium? Under gravel? Wet/dry? DIY…. yes, yes, yes. We have two rules though. 1) If water is being forced through the media there should be mechanical filtration prior to water hitting the MarinePure. (Floss, sponge, sand filter, etc.). MarinePure would act as a great mechanical filter, but it would clog in this case and MarinePure is too costly to frequently replace. The best method is to use a mechanical filter to get the gunk out before it even has a chance to break down into ammonia. If MarinePure is placed in a spot where water is allowed to flow around, not pushed through, then mechanical filtration probably is not needed.

The other rule is that it should not be allowed to move. (Do not place in an up-flow reactor). It will wear on itself and turn to dust in no time.

The next consideration is placing it in active or passive flow. We consider active flow where the media is directly in the path of water flow.

In this case, oxygenated water will be forced deep into the media. This might limit the regions available for “low oxygen” anaerobic nitrate reduction to occur.

Moving it to a low-flow area or blocking off a couple of sides of the media so water needs to come from farther away through the media, can allow for larger regions within the media to become anaerobic. We recommend this method when hobbyists really want to drive their nitrates low.


How much to use?

Our recommendations on usage amounts are both scientific and experience based, and we feel, are very conservative since EVERY system is different. There is no reason to have too little biofilter media.

For ammonia and nitrite control, in an active flow location, 1 MarinePure BLOCK, or 1 gallon of MarinePure SPHEREs, will filter 500 gallons of aquarium water. The same amount of media in passive flow, where nitrate reduction is the main goal, will filter about 100 gallons of water. Every system is different, both in setup and bio-load, so feel free to reach out to us to discuss your application.


Where to get it. 

MarinePure is available worldwide. Check out our website to see if there is a distributor in your country.

In the USA and Canada, there are many distributors supplying your local fish stores, please support these stores when possible. If your favorite store does not carry MarinePure, ask them to reach out to us and we can help them determine the best ways to obtain it.

Here is a review from Garth Barber in 2013, that hit on many of these issues surrounding biofilter media probably explains it better than I did…

Learn More About CerMedia and MarinePure®


CerMedia LLC, located in Buffalo, New York, manufactures MarinePure® Bio-Filter Media. MarinePure is a man-made ceramic bio-filter media that has the unique combination of a high surface area plus network of open-flow pores. These features enable water to move easily throughout the part, allowing the nitrogen components to find both the aerobic and anaerobic bacteria, allowing all parts of the nitrogen cycle to take place, including ammonia and nitrite elimination and nitrate reduction.

If you have any questions about how to access MarinePure® Bio-Filter Media or incorporate into your new or current tank, feel free to reach out to us. We’d love to help walk you through how to use this bio-filter media for a cleaner, easier-to-manage fish tank.




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Contact us to learn more about how MarinePure and BioVast can help your aquarium and aquaculture environments!


P.O. Box 600
66 River Rock Dr.
Buffalo, NY 14207
USA or

(716) 549-6600

Leyda Vazquez
Business Development Manager
(716) 549-6600 x264

Paul Pustulka
General Manager