FW Chemical Filtration (CARBON)

[akapaul26]

The use of chemical filtration (carbon)

The most commonly used chemical filtration methods is Activated Carbon.There are also other products that fall under the heading of chemical filtration. Products like ammonia chips, designed to remove ammonia from the water. People who have excess nitrates might use ammonia chips to slow nitrate production. Nitrates are not considered harmful in general, but an excess of nitrates is undesirable, particularly in salt water aquariums where nitrates must be kept very low. Other types of chemical filtration is BioChemZorb by Aquarium Pharmaceuticals. BioChemZorb comes in a sealed filter bag, ready to rinse and place in a filter. It normally lasts about 6 months. BioChemZorb not only cleans water but also polishes it.

Now there are a variety of pollutants dissolved in any aquatic environment containing biological life. Dissolved ORGANIC compounds (DOC's) include proteins, amino acids, phenolic compounds, pheromones and other metabolic byproducts which are continuously being exhausted into the aquarium water by the fish or other aquatic animals.

If these organic substances are allowed to become concentrated, they will negatively impact fish, feeding rates, growth rates and reproduction rates, they will lower immune system activity and promote blooms of pathogenic bacteria in the water.

These DOC's can be controlled by water changes, however a pretty rigorous maintainance schedule is required. I recommend maintaining your nitrate levels at less than 10 ppm since doing so will concurrently facilitate a low level of DOC's, something which you cannot test for. The problem is that a great many aquarists don't adhere to such a maintenance schedule and don't test for nitrates.

If you are not managing your nitrates and thus your DOC levels, chemical filtration may be the best method for you. Carbon filtering removes DOC's via adsorption. As the aquarium water flows through the carbon medium, the DOC'S come into contact with the surfaces of the carbon granules where they become attached, this is called ADsorption --- not ABsorption. Some DOC's are adsorbed directly, but others combine chemically with already-captured substances. When the surfaces of the carbon become saturated, it stops working and needs to be replaced with new carbon.

Thus, carbon does exhaust over time and needs to be replaced regularly. The effectiveness of activated carbon includes:

1. Adsorption: static forces that attract particles to the carbon which allows the particles to be consumed by Bacteria that settle on the carbons surface.

2. Diffusion of gases: This process includes particles absorbed into the carbon that are turned into gases and detoxified (02 into 03).

3. Chemosorption: Particles are irreversibly bound to the carbon it self.

So how much carbon should be used? Research suggests that generally, there needs to be 4 to 10 grams of granular activated carbon (GAC) for every gallon of water depending on stocking density. It can be hard to determine the correct amount of carbon if the tank is over stocked. Ther are also other determaining factors that can effect the amount of carbon to be used.

Look for activated carbon which is phosphate free. A great many carbon grades are washed with phosphoric acid in an effort to support the adsorption sites since this is cheaper than degassing. This phosphate will leach into your aquarium water and can reult in a major algae problem. Most carbon in pre-made cartridges is of low quality,if carbon is going to be used i would recommend not using the pre-made cartridges.

Carbon absorbs most aquarium medications, especially antibiotics. Carbon should be removed while medicating so don't forget to put it back in when tank treatment is finished.

Carbon can deplete some trace elements needed for plants to grow. It should still be used to adsorb organics but only on a montlhy basis and only for 5-7 days.

If your filter uses prepackaged cartridges containing carbon, realize that these cartridges typically contain poor quality carbon and if quality carbon is used, only 20 percent or less of the recommended amounts of GAC is present. You can slit open the cartridge and fill them with more GAC but many pad filter types simply will not hold that much. Thus, the carbon in the vast majority of filter pads on the market simply is not functioning.

In a filter, the GAC should always be placed after the mechanical filtering medium otherwise, the particulates in the water will quickly coat the surfaces of the GAC, rendering it useless.

So what's the bottom line? If you're going to use activated carbon, you've got to use QUALITY material, you've got use ENOUGH of it to work and you've got to CHANGE IT often enough to keep it functional. The use of chemical filtration should never replace regular water changes in fact a regular water maintnance schedule is necessary.

[OrionGirl]

Are you going to add info on other chemical filtration options?

[joephys]

I kind of agree, with the title, more types of chemical filtration should be listed, or the title changed to reflect carbon.

All in all, I think its a pretty good article. I am not quite sure I agree with the phosphate=algae issue. I think its a myth that came from salt water tanks which do get bad algae blooms from phosphates. I and many others have very high phosphates with no algae. Not a huge deal and not proven, just an observation I and others have made.

In my opinion, as written, some people might think that carbon is a way to get out of doing water changes. I know that wasn't your intent, but people can tend to twist meanings to fit what they want to believe.

I like that you explained it was adsorption and absorption. I also like the explination about how you can somewhat infer other DOC's from nitrates, but nitrates are not a direct accurate measure of them. Its an important issue for people to understand.

All and all I think its a pretty good article.

[akapaul26]

Thank You for your input and hope everyone who has questions about chemical filtration can become more knowledgable by reading the article.
Thanks,
Paul