The stock filtration system of a Fluval Spec series aquarium comes with three components of filter media. They are:
- Mechanical Sponge Filter – this is the foam filter block that fills most of the filter section. In it are two holes that house the other two filter media that come with a Fluval Spec (or EVO) Aquarium.
- Biological Filter – This is a bag filled with ceramic rings. They are porous and have lots of surface area. The function of all this surface area is to provide a place for the beneficial bacteria to grow.
- Chemical Filter – This is a bag filled with activated carbon. Activated carbon has lots of surface area like the ceramic rings. In addition, it has the ability to remove some dissolved orgaincs and toxins.
Advantages of Using Activated Carbon in an Aquarium:
Some of the organics and toxins that activated carbon is claimed to remove include: bleach, chlorine, odors, and pesticides. Activated carbon has special use in removing medications. Once you are done with a dosing regimen to rid your fish of disease, carbon usage can be helpful to remove the remaining chemicals and get your aquarium back to a steady state. If you choose to not use the carbon bag in your spec, make sure to keep it stored for such a time.
Disadvantages to Using Activated Carbon:
A few notable things that it won’t remove include nitrite and nitrate, two byproducts of a new aquarium that is not yet stocked with beneficial bacteria. So while it will help your water quality a bit, it will not work wonders and alleviate the root problems of an uncycled aquarium. Some people use activated carbon to keep odors at bay. This goes back to a root cause problem. Our aquarium, in it’s admiditally young life (10 months) has never smelled bad. This is probably in the Too Much Information category, but i have taken the nasty water that I clean out the sponge filter, which is fully saturated in brown detris, and smelled it. It actually is quite inert and has very little smell. (I had my wife test this as well to verify it wasn’t just that I have no sense of smell.)
The big disadvantage that has kept me from considering ever using the activated carbon bag in our spec is that it removes trace elements. We have setup this aquarium as a low light planted tank from the start. Part of the care for a planted aquarium is to provide fertilizers to the water column. There would be no use in placing activated carbon in a planted tank as it would remove the very trace elements that the plants are using.
Another big disadvantage to activated carbon media is the cost over time. It can absorb material to the point where it can not absorb any more. At that point, it needs to be replaced. While the cost of replacement bags of carbon for the Spec line of aquariums is reasonable, it will add up over time.
Alternatives to the Activated Carbon Bag in the Spec Filteration System:
I think that having lots of surface area in the way of more biological media is much more beneficial than anything activated carbon can offer. If you have a proper beneficial bacteria colony growing in your filtration system, that will probably take care of any issues you would run into with water quality. I would first suggest to all aquarist to not use the carbon bag and instead use two bags of Biomax. This is what I started out with and it worked great.
Since then I have transitioned to using Seachem Purigen in our aquarium. I use the stock foam filter block with a bag of Biomax in the top section and a 100ml bag of Purigen in the bottom section (folded over in half to fit). That has been a very nice setup; the water is usually extremely clear. As I said earlier, I have never had odor problems and all the fish/shrimp/snails are healthy.