No announcement yet.

Matrix vs Pumice

  • Filter
  • Time
  • Show
Clear All
new posts

  • Matrix vs Pumice


    I was wondering if Seachem can clarify a few things about Matrix. I have been investigating and some believe that Seachem Matrix is just cleaned sterilized Pumice. Is this true? If so do you add something to it so it denitrifies Ammonia, Nitrite, and Nitrate? I would rather hear this from the source of who makes it...then what everyone seems to think in other forums and online. Because if it is just can it be claimed that it does something different then other medias that just grow bacteria that breaks down Ammonia and Nitrite like pumice? But Matrix is supposed to remove Nitrate levels as well. Please explain and thank you for your time.


  • #2
    Re: Matrix vs Pumice

    This isn’t the first time we’ve been asked this question. The short answer is you know what you are getting with Matrix: it has been tested and proven to work well as a biomedia. We’ve tried to find a better biomedia and so far have been unable to. With garden center pumice, you have no guarantee about whether or not it will support denitrifying bacteria or whether it will affect pH or leach anything into the tank.

    For more detail, here's the longer explanation:

    I understand why people look at Matrix and compare it to the pumice they can find at the garden center; they are both porous stones. The difference is that not every porous stone is the same; Matrix is a specific type chosen for its porosity, pore size, durability, and inert nature. When you buy Matrix, you know what you are getting. It has been tested in the lab and in thousand of hobbyist's aquariums for more than a decade with excellent results. You aren't just purchasing the physical material when you buy a container of Matrix; you are purchasing the research which has sourced and tested this specific type of stone, and the assurance that it is safe for use in your aquarium. You also get support when, like now, you have questions about the product or if you need aquarium advice. You can't buy any of those things at a garden center or rock yard.

    One thing to think about with anything that goes in your tank has to be whether or not it is safe. The term pumice includes many types of stone and not all of them have the same porosity or same chemical makeup. With Matrix, you know it isn’t going to affect your pH or leach anything into your tank.

    Matrix certainly isn't the only biomedia you can choose. Beneficial bacteria will grow on almost any submerged surface and people use everything from plastic scrubbing pads to sintered glass media. Each has pros and cons, and can be judged on a few critical criteria to choose the best for use in our filters.

    The first consideration is going to be surface area. The greater the surface area, the more bacteria that can colonize the biomedia. Providing surfaces to colonize is the main job of any biomedia. Second we have to consider what kind of surface area the biomedia provides: internal or external? A biomedia like bioballs increases surface area for bacteria to colonize, while allowing water to flow freely through it, but all of the surfaces are external; aerobic nitrifying bacteria can grow quite well on them, but can easily be disrupted if rinsed or exposed to air for too long. Porous biomedia like Matrix or any of the stone, ceramic, or sintered glass media are going to also have some internal surface area. This will increase the available surface for bacteria colonies while also providing some protection to them against being washed away or dried out during filter maintenance.

    The size of the pores in the medium is also important. The larger the pores, the smaller the surface area. In the other direction, if the pores are very, very small; then the surface area might be great but then won't work as well as a biomedia because of bacteria not being able to grow in the small volume inside the pores and the decreased efficiency of fluid transport. We have compared Matrix to other popular biomedia (in this study: and described on the Matrix product page: ), and both of the compared biomedia had pore diameters in the range to be biologically useful, but Matrix had 4 to 9 times the biologically active surface area compared to the other media. All pumice is porous, but pore size and density varies greatly, and you have no guarantee of the size of those pores when you buy some intended for other uses.

    Another consideration is durability and maintenance. Matrix is an inert, porous stone which is extremely durable, and because most of the surface area is internal, it can be rinsed without destroying all the beneficial bacteria.

    One of the advantages of Matrix versus many of the traditional biomedia is that the densely porous interior space allows for anaerobic denitrifying bacteria to colonize and remove nitrates. Some sintered glass media claim to be able to also support these colonies based on the same principle but it needs to be used at a lower flow rate to support denitrifying bacteria and works best in lower light levels. In comparison, Matrix can support denitrifying bacteria even in high flow situations and works fine even in well lit conditions. With pumice from the garden center, you don’t have any information on how well it will perform in this aspect. We are always looking to improve our products, but so far we’ve been unable to find or develop a biomedia that works better than Matrix.

    There are other good biomedia on the market or do-it-yourself options, but Matrix has stood the test of time and works exceptionally well. It is by far the best biomedia I’ve ever used. While it is easy to set up visual comparisons and hold it up next to cheaper pumice, the proof is in its performance in the aquarium.


    • #3
      Re: Matrix vs Pumice

      Thank you for the detailed explanation. I now have no doubt I am going to try Matrix. I am very excited. Do you have any suggestions on pre-rinsing Matrix before putting it into a canister filter? I have read if you don't do it well enough you c get a chalky film and foggy water.

      Also is all of the stone in Matrix the same? I have also read some people saying that there seems to be different types or different colored stones/media in the container. Thanks again for your time.


      • #4
        Re: Matrix vs Pumice

        It is good to rinse it before adding it to the filter as there can be some dust on it.

        Most of the stones will be the same but as it is a natural material, there is some variation and there might be some stones that are different. This won't negatively effect the way the product works.


        • #5
          Yes make sure you rise I bought a bucket 4liter of matrix and no where on the bucket does is say it needs rinsed but I did because I figured it would be best because of dust and maybe a few random rock luckily I did rinse because little did I know if I didn’t rinse I would have killed all my fish there was about 1 liter of the bucket that was not pumice and a little Suprise In there a bullet I have emailed seachem support Saturday and still am waiting a reply
          Attached Files


          • #6
            Rinse sorry


            • #7
              Hello Jmacke! Thank you for getting in touch with our support team about this. Unfortunately even though we do our best to carefully QC the product, it is a naturally mined media so sometimes anomalies occur. Again, we sincerely apologize, and thanks for reaching out to us!