Are Bio Balls a “Nitrate Factory”? Plastic vs. Non Plastic Bio Filter Media: What is the Difference?

September 29, 2017 Phil Overton

Plastic Bio-Balls vs. Ceramic Bio Filter Media?

In the aquarium hobby, we often hear that Plastic Bio-Balls are “Nitrate Factories” in that their use results in high aquarium nitrate levels. Hobbyists are concerned other bio filter medias might have the same issue.

In this blog, we will discuss how Plastic Bio-Balls are really doing their job, although poorly (in our opinion), and how ceramic bio filter medias do not have the same problem as plastic bio filter medias. The information below will help you better understand the difference between plastic vs. non-plastic bio filter medias.

The important takeaway to understand is just because you have high nitrate levels in your fish tank, does not mean you have created a “Nitrate Factory” that you can’t get rid of. Let us help you understand why!

Common questions you might ask your

  • Why Are Plastic Bio-Balls Considered “Nitrate Factories”?
  • How Is Ceramic Media Different Than Plastic Media and Not A “Nitrate Factory”?
  • How Does MarinePure Compare To Plastic And Other Bio Filter Media?

Why Are Plastic Bio-Balls Considered “Nitrate Factories”?

Complaining that Plastic Bio-Balls are “Nitrate Factories” is a little unfair to Plastic Bio-Balls.

As an aquarists, you already understand, managing the nitrogen cycle is a vital part of maintaining a healthy aquarium. Aerobic bacteria or those that use oxygen to convert ammonia to nitrite and nitrite to nitrate perform in an oxygen rich environment. This usually occurs at the outside surfaces of media, or in higher flow systems, deeper in the media if the media has an internal pore structure.

Aerobic bacteria will only convert ammonia to nitrites and nitrites to nitrates. In order to reduce nitrates, anaerobic bacteria are required.  These bacteria perform in low oxygen environments where the nitrates can be converted into harmless nitrogen gas.  This gas can then escape your aquarium.  Again, anaerobic bacteria perform in low oxygen zones.  These low oxygen zones are made by oxygen being used up during the ammonia to nitrates conversion, therefore, it must occur deeper in media.  The surface area of Plastic Bio-Balls is all external and hence, always exposed to oxygen rich water.  It can convert ammonia to nitrate, but can go no further. There is no opportunity for anaerobic bacteria to develop in the media.

Since plastic media cannot complete the full Nitrogen cycle, they are considered “Nitrate Factories” and nitrates will rise in the aquarium. The plastic media has done its job as intended, converting ammonia to nitrates. Unfortunately that leaves the hobbyist with high nitrates, needing another way to lower nitrates.  Lowering nitrates can be frustrating and costly as this often involves water changes or complex filter designs and maintenance. Also, since the amount of surface area is limited on plastic media, their capacity to reduce ammonia is low, and often there is a buildup of bio-film requiring cleaning.

How Is Ceramic Media Different Than Plastic Media and Not A “Nitrate Factory”

Plastic Bio-Balls are considered “Nitrate Factories” because they do nothing to complete the final stage of the nitrogen cycle, converting nitrates to nitrogen gas.  Ceramic bio filter media can take the process to this final step.

Ceramic media (including live rock), contains internal surface area. There can be zones inside the media where oxygen has been used up by the ammonia to nitrate conversion. In these pockets of low oxygen anaerobic bacteria can grow. These are the areas that will help to control your nitrates. Hobbyists see results ranging from nitrates that are just not raising as quickly, allowing for less frequent water changes, to being nitrates almost non-detectable.

How Does MarinePure Compare To Plastic And Other Bio Filter Media?

MarinePure™ bio filter media, made by CerMedia LLC in Buffalo, NY is an advanced ceramic media.  The surface area of ONE MarinePure Sphere is equivalent to the surface area of 1,350 Plastic Bio-Balls.  That is almost 18 gallons of Plastic Bio-Balls.


MarinePure bio filter media is NOT a “Nitrate Factory”.  It provides a nice comfy oxygen enriched home for the types of beneficial bacteria that thrive on ammonia and nitrites. It also has pores within the structure with what we like to call “nooks and crannies” that allow for low oxygen zones. Soon enough, the anaerobic bacteria is able to move in and begin consuming nitrates. Plastic Bio-Balls do not contain these “nooks and crannies” as all their surface area is external and exposed to oxygen.

MarinePure is different from other ceramic bio filter medias in that it also contains an interconnecting system of open pores that allows water to flow throughout the media. This makes the entire part available for beneficial bacteria growth, far beyond what is generally available in standard ceramic media or live rock.

TABLE 1.  Properties of Plastic, Ceramic and MarinePure Bio-Filter Medias

What Now?

MarinePure is a bio filter media that is highly regarded by hobbyists. We take pride in our media producing effective results. The reason for this article is to answer a question we often hear, “Will MarinePure Spheres become “Nitrate Factories” like Plastic Bio-Balls if I use them in my aquarium?” With that, comes along the idea of understanding the difference between plastic and ceramic bio filter medias.

If you would like to further reduce nitrates, the MarinePure BLOCK has been specifically designed to reduce nitrates.  By putting this 8 by 8 by 4 inch block in a low flow area of your sump, you’re giving the internal structure plenty of opportunity to develop a large anaerobic zone to really make an impact on your nitrate levels.

CerMedia LLC is pleased to help hobbyists worldwide. To find out where to purchase MarinePure, visit our website today.

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