The importance of filter media.

By: Carlos Coe


The importance of filter media.

For the beginning hobbyist, you’re going to be seeing and reading a great deal about filter media. Hand in hand with what should be prominent in your research, fishless cycling, proper filter media is a crucial component to maintaining healthy water and subsequently, healthy fish. It can seem a bit overwhelming and confusing at first, but rest assured, I will try and give you vital information and insight into what makes your filter work. One thing before I go on, I feel it is important to add that many companies as well as local pet store employees advise you change and replace your filter media monthly. This is absolutely false and a way to continuously get business. Filter media, if properly washed, can survive months and months at a time. NEVER discard your filter media unless it is physically decomposing. Doing so will nearly destroy colonies of bacteria that have built up in your aquarium.

Now, for the sake of simplicity, I am going to explain what exactly filter media does. Whether you have an air powered or electrical filter, water is drawn through a pump and passed through the media. During this process, we see two things being removed from our water. One is physical debris, such as flakes of food, waste, and dead leaves. The second is dissolved waste, which is primarily ammonium, the fish equivalency of urine.. Now, something we need to take it to account here is that if your filter is moving slowly, it has pulled in too much debris and clogged. If your filter is clogged, your water filtration is greatly reduced. In order to combat this, monthly (at maximum) cleaning of the media is required. This can be done by lightly rinsing it off in a bucket of AQUARIUM WATER ONLY! Tap water will kill your bacteria.

Filter media is divided into three categories, each of which fulfills a certain task. The first category is mechanical filtration, which removes solid wastes. This is typically seen in the form of a fine, or a coarse, sponge. The second category is chemical filtration, which breaks down and neutralizes harmful chemicals. This is typically seen in the form of activated carbon, or mineral rocks used to activate an agent that binds to ammonium, breaking it down. The third category is biological filtration, which supports the bacteria that dissolves the harmful chemical waste.

  • SpongesA common medium of mechanical filtration is a sponge. The majority of internal and external use a variety of sponges, or even two, one harsh, and one fine. The rule of thumb is that the coarse sponge be placed so that the water initially passes through it, and the fine sponge be the last thing the water passes through. The sponge utilizes it’s ability to soak and hold debris, which subsequently results in a beneficial bacteria growth. This growth is key to any functioning aquarium as it will be the driving force in your filter. Now, one key fact to remember is that a sponge must ALWAYS be washed in aquarium water. As previously noted, if you wash your sponge in tap water, the beneficial bacteria will be destroyed by the chlorine and various other chemicals.





  • Filter WoolThe effectiveness of filter wool can be utilized in a variety of ways. Commonly, filter wool is used as a cleaner upper of sorts, ensuring the water that passes through it comes out crystal clear and clean. It is also effective as a form of mechanical filtration if loosely packed. It acts as a sponge, soaking up debris and physical waste. If it is packed tightly, it is able to support the growth of surface bacteria.

  • Chemical Media (Activated Carbon, charcoal, etc)Chemical filtration removes dissolved particulates from the aquarium via activated carbons, resins, and other adsorbents. We see this in the form of ammonia nullifying chemical media, activated carbon, charcoal inserts, and more. Now due to the fractured surface of the chemical compounds, we often see the build up of particulates which results in mutually ineffective chemical filtration. Because of this, things such as activated carbon are slowly being phased out of the common filtration setup, due to their inability to sustain consistent adsorption.

  • ZeoliteZeolite is a mineral that binds itself to ammonium. As previously stated, ammonium is the equivalent of fish waste, which eventually results in ammonia, so this is has to be a good thing, correct? Well… not so much.


    Ammonium that is chemically removed cannot be used to feed and promote the growth of bacteria. So if you’re using Zeolite in an immature aquarium, this is going to be counterproductive, further delaying your cycle. Secondly, Zeolite becomes quickly saturated. If this happens and a viable biological filter isn’t present, the ammonium will build up and eventually poison your fish! A healthy biological filter is often regarded as far more effective than Zeolite.

So you’ve covered a few basics, but how do I choose?

Well, the ideal functions are biological and mechanical. A good amount of quality sponges, and maybe just a months worth of something like activated carbon, should promote the growth of effective bacteria while nullifying any unwanted chemical substances. The majority of chemical filtration however can be seen as a “bonus” of sorts and may or may not help your aquarium. With proper maintenance however, you may see progress with this type of filtration.

I hope I have given a beginner hobbyist an idea, if not even a small one, about filter media and how it works. I can only leave you with one thing. RESEARCH! The more you know, the higher your rate of success!

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