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activated carbon filters

This is a discussion on activated carbon filters within the Beginner Freshwater Aquarium forums, part of the Freshwater Fish and Aquariums category; --> Thanks all! i've decided to remove the carbon from my filtration system (not that the carbon I have in there now is probably good ...

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activated carbon filters
Old 01-25-2010, 09:38 AM   #11
 
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Thanks all! i've decided to remove the carbon from my filtration system (not that the carbon I have in there now is probably good anymore, since its been there since mid-october). Also, have some real plants, that are doing rather well now, with the presumably "dead" carbon.
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Old 01-25-2010, 11:06 AM   #12
 
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Quote:
Originally Posted by mrdemin View Post
I use carbon, its such a pain to remove it from the filter pads that I use.

I have my tank up since around Oct, and have been running activated carbon since... I don't think anything will be different if I stop using it.
You are correct. If you are just using carbon in the small quantities that come in the filter pads, you will not notice anything. On the other hand, if you are using bulk carbon inside a canister filter, or a large carbon bag such as what fits inside an AquaClear, then you will see a difference.
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Old 01-25-2010, 01:19 PM   #13
 
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I use the same filter as you on my 55g and haven't used it since day 1
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Old 01-25-2010, 04:44 PM   #14
 
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Mark, what do you know about re-activating carbon? I've seen a lot of references to carbon re-activation by drying it out on a cookie sheet in an oven at low temperatures. Is there any truth to this, or are you better off just replacing your carbon with fresh? I'm kind of skeptical as to how an oven could bake off things like heavy metals.
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Old 01-25-2010, 04:48 PM   #15
 
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Originally Posted by iamntbatman View Post
Mark, what do you know about re-activating carbon? I've seen a lot of references to carbon re-activation by drying it out on a cookie sheet in an oven at low temperatures. Is there any truth to this, or are you better off just replacing your carbon with fresh? I'm kind of skeptical as to how an oven could bake off things like heavy metals.
My understanding, which I just confirmed with a quick read of Moe, is that reactivating carbon is not really worth the effort. You can extend the life slightly, because some of the organics are literally baked off the surface, exposing some pores. But this is minimal and not worth the time or benefit.
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Old 01-25-2010, 06:57 PM   #16
MOA
 
Pasfur,

I used to work at the laboratory of the College of Southern Idaho and activated carbon was one product we test for the aquacultural department. We found that in a non-biological solution activated carbon does absorb most organic compounds provided they are broken down to the right size along any break-down process they might encounter that exposes them to the external environment (many peptides, when broken down biologically, skip over the correct region and jump straight to ammonia, which activated carbon does not absorb all that well due to its small size). Thus, activated carbon initially appeared to be a suitable filter material for the aquacultural department to use.

Shortly after implementation, however, some of the orginal problems with nitrogen compounds returned. After testing activated carbon in biological solutions (with live bacteria) it was found that tthe bacteria either broke the organic substances down too quickly to be adsorbed by the activated carbon or the bacteria were actually able to pull the organics off of the activated carbon directly (thus re-releasing the substances' byproducts back into the water). After half a year of testing, it was determined that a biological system wound up operating almost exactly the same with or without activated carbon. At the lab, we did several head-to-head comparisons and found that activated carbon made little difference unless used in very large quantities (up to 6.8 ounces per gallon (1.8mL/L)) and was changed frequently (once a week). All of the systems proved cheaper to operate long-term with purely biological filters and frequent water turnover (partial water changes).

In my experience, activated carbon looks really good in the lab, under sterile conditions, but is useless in a living system. It does have some valid uses (removing medication, for example), but it is not really all that practical in a dynamic system.

MOA
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Old 01-26-2010, 08:35 AM   #17
 
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Originally Posted by MOA View Post
I used to work at the laboratory of the College of Southern Idaho and activated carbon was one product we test for the aquacultural department.

After testing activated carbon in biological solutions (with live bacteria) it was found that tthe bacteria either broke the organic substances down too quickly to be adsorbed by the activated carbon or the bacteria were actually able to pull the organics off of the activated carbon directly (thus re-releasing the substances' byproducts back into the water).
MOA
As much as I appreciate your background and value your input, you are talking about a study that would change the entire aquatics industry. If this study was conducted and documented properly, then you have a responsibility to publish the study and submit it to the proper hands to result in changes being made. These things generally start at the public aquarium level, in the hands of people such as Charles Delbeck of Coral Magazine.

Such a result needs the opportunity to be discredited, especially when you are discussing a concept that goes so heavily against the mainstream. For example, I can see 2 issues that need to be addressed in your study.

1) If the water flows through the activated carbon prior to entering the biomedia, then the bacteria do not come in contact with the organics to have the opportunity to be broken down. Filter systems today are designed to achieve this. For example, look at the Marineland hang on units. All water is forced to flow though an activated carbon cartridge before being process biologically by the biowheel. In canister filters and sump systems, carbon can be placed before the biomedia.

2) If the bacteria is so efficient at breaking down organic waste prior to it being removed by activated carbon, the benefits of a protein skimmer a marine system become highly suspect. A recent study in Coral Magazine was published showing the percentage of organic compounds removed with different brands of skimmers. The results were very positive. This contradicts the results of your study, which appear to state that bacteria are so efficient that organics do not have the opportunity to be removed by other means.

Granted, carbon has to be changed on an appropriate schedule. Additionally, most hang on filter units do not have an adequate amount of activated carbon. However, all equipment has to be used properly. We would not judge a light bulbs effectiveness on a live plant tank if the bulb were 18 months old. In the same was, we can not judge activated carbon that is 4 weeks old. It has to be changed at the proper time, and used in proper quantities.

For the record, your statement that 6.8 ounces per gallon needs to used falls short of providing all the correct information. The amount of carbon necessary would depend on the amount of waste being produced in a given system. Far less, or far greater amounts, of carbon may be found to be ideal, depending on stocking levels and other nutrient inputs and exports.
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Old 01-26-2010, 08:36 AM   #18
 
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Originally Posted by LisaC144 View Post
I use the same filter as you on my 55g and haven't used it since day 1
What do you use in place of the carbon? Do you put anything in to fill the space?
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Old 01-26-2010, 10:22 AM   #19
MOA
 
Okay,

1) Bacteria do not just live in the biological medium--they live all over in a mature biological setting. The problem we encountered in our testing was that the bacteria would actually colonize the activated carbon, thus often encountering the organics before or at the same time that the carbon was supposed to be adsorbing them. We found that this issue could be circumvented by changing the carbon every couple of days, to keep the colonies from growing, but such proved rather impractical to maintain. The net effect is that if the carbon is placed in the biological environment more than a few days, its position relative to the biomedia will not matter much.

2) This data has little impact on protein skimmers as they operate on a different principle than activated carbon. Activated carbon is limited by its pore size and the fact that it does not actually remove the substances from the water flow (meaning that bacteria can still get at the substrate). Protein skimmers, on the other hand, usually do not have much in the way of substrate and also remove the organics from the system completely so that there is little chance as to reintroduction of the material. No less, we did test protein skimmers at one point and did find that their efficiency dropped when used in tanks with a high level of porous substances which the bacteria could colonize, but not by enough to be truly significant.

"Granted, carbon has to be changed on an appropriate schedule. Additionally, most hang on filter units do not have an adequate amount of activated carbon. However, all equipment has to be used properly. We would not judge a light bulbs effectiveness on a live plant tank if the bulb were 18 months old. In the same was, we can not judge activated carbon that is 4 weeks old. It has to be changed at the proper time, and used in proper quantities.

For the record, your statement that 6.8 ounces per gallon needs to used falls short of providing all the correct information. The amount of carbon necessary would depend on the amount of waste being produced in a given system. Far less, or far greater amounts, of carbon may be found to be ideal, depending on stocking levels and other nutrient inputs and exports."


We took to changing the carbon weekly and in fairly large proportions, as mentioned before. We were not judging activated carbon that was "4 weeks" old. Secondly, I agree that the waste level should make a difference, and it does, but the result of 6.8 ounces/gallon was obtained with a solution whose organic content was between 2.5E-8 and 5.0E-6 molarity--less than the equivalent of 5ppm nitrate when the organics are processed. Frankly, we did not want to test any higher concentrations because we simply could not afford the expense of that much additional carbon. If it took so much carbon at even such a low concentration, then, extrapolating, it would be reasonable to assume that very high levels of carbon would be needed for higher levels of organics--quite impractical.

As to the research, I will see if I can dig it up for you.

BTW, thank you very much for listening--your patience is remarkable and I must admit I am somewhat envious :).

MOA
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Old 01-26-2010, 10:53 AM   #20
 
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No, I just use the sponge and biomax. You could put in an extra biomax if you want for more beneficial bacteria, but I never found the need to. My tank is well established and ding just fine with the sponge and 1 biomax. If the carbon is unused, keep it on hand if you ever need to medicate. Carbon removes medication from the water. If it's used, you can always buy carbon IF and when it is ever needed.
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