carbon

[chompy]

I have always been told to not use carbon because it will release toxins it has absorbed before hand. Is this true or is it anouther reason why we don't use carbon?

[pcsb23]

Tyler,

Carbon in itself is not a bad thing. There is no need to continually use carbon, particularly with the higher water change regime normally associated with keeping discus.

Carbon is indiscriminate in what it absorbs, ie it absorbs good things as well as bad things, in soft water the trace elements that are essential to all fish will get absorbed quickly and will adversly affect the fish.

Carbon should be used where you wish to remove meds and if you suspect a toxin has been released into the water say from an aerosol (like fly killer spray). Although both effects can be achieved with water changes.

hth,

[chompy]

Thats what I thaught, but I was just told otherwise by a few people which made me second guess myself

[mickeyG]

pcsb23 is exactly right. If you have a need for carbon like removing toxins, metals, meds, it is ok to use periodically. But like he says, once the carbon is full (all the surfaces have stuff on them), it will begin to release those back in the water.

So you need to remove/replace the carbon before that happens.

Michael

[lhforbes12]

I have to somewhat disagree. Activated carbon should not release anything that it has trapped. btw it works by aDsorption not aBsorption (a sponge absorbs things, actived carbon works in an entirely different way. Particles are attracted to the micro pores in carbon and are trapped there), Having said that I do agree that it isn't needed normally. It has two things which are detrimental to an aquarist IMO
1. For carbon to work properly water must flow SLOWLY past it. Almost none of us have flters which have a slow enough flow for carbon to be truly effective.
2. Cost. Carbon is just cost prohibitive, it fills very quickly and is no longer useful in a very short time (far shorter than the month or so that most users keep it in their filters).

It is excellent, as Paul already said, for removing medications. It is also useful in removing DOCs (Dissolved Organic Compounds). However, also as Paul has already stated, wc's are usually a much better solution to both of those problems.

Larry

[mickeyG]

Larry,

I don't know that carbon leaches back for sure never having used it. My opinion is based on others. I will say that I have been reading all the techy stuff about aquariums for about 5 years and the predominant (I bet 75% or more?) of the opinions (many from the leaders in the industry & books) is that when the carbon is full - it will release some of its load back into the water.

I can't give you the actual data how or what they base their opinions on, but I'll try and take the time to read more and then repost.

As far as the price being prohibitive - I have to somewhat disagree. I bought 1.87L of marineland black diamond carbon on the net for $9.99. It looks like a ton. I thought I would use it in a little corner filter in my water mixing container but decided not to use it. But if I used it all the time it would last a year or more. I admit I only make 20g of water twice a week, but unless you have hundreds of gallons, it wouldn't be THAT expensive.

Michael

[lhforbes12]

Larry,

I don't know that carbon leaches back for sure never having used it. My opinion is based on others. I will say that I have been reading all the techy stuff about aquariums for about 5 years and the predominant (I bet 75% or more?) of the opinions (many from the leaders in the industry & books) is that when the carbon is full - it will release some of its load back into the water.

I can't give you the actual data how or what they base their opinions on, but I'll try and take the time to read more and then repost.

As far as the price being prohibitive - I have to somewhat disagree. I bought 1.87L of marineland black diamond carbon on the net for $9.99. It looks like a ton. I thought I would use it in a little corner filter in my water mixing container but decided not to use it. But if I used it all the time it would last a year or more. I admit I only make 20g of water twice a week, but unless you have hundreds of gallons, it wouldn't be THAT expensive.

Michael

Michael,
This is actually precisely why I decided to address the issue. As you can tell I agree fundamentally with what Paul said. Except that carbon can not possibly leach things back into the water column. The reason is because carbon is not a sponge. It does not work that way. Carbon chemically attracts ions to itself (think of it as a magnet) there is simply no way for it to leach back things once it has them other than to reverse the ionic process, which is something that is so unlikely that it borders on the impossible. As to cost, if you read what I said, and perhaps I didn't say it well enough, for carbon to remain effective you would need to replace it every two days or so, so I stand by my orignal statement, it is cost prohibitive.

Larry

[Graham]

Hi Guys this is my 1st post here and I haven't had discus in 30+ years, but Tylers orginal question was due to my disagreeing with him on our local board that AC released it pollutants back once it was exhusted/spent...full.


I fully agree with Larry...it cannot happen. The pollutants are chemically bonded to the carbon and for them to be released it takes acids, steam or extreme heat...like 1500*F...not many things that are available in an aquarium or a pond. AC has it's place in the hobby but it's not required on a regular basis.

Now if it's acting as mechanical media then it probably would dislodge some fines when distrubed.

Regards Graham

[Alight]

No reactions are one way. They are always bidirectional. Sometimes one direction is greatly favored. Acids are plentiful in a Discus tank, as they are constantly made by the nitrification process, and can interact with the carbon to produce a more favorable reverse reaction, depending on how much nitric acid is in the tank, and how much of the ions have been adsorbed. Once the carbon is "full" of adsorbed ions, it is much more likely that ions will be "lost" to the tank water, than when the carbon has a deficit of organic ions.

[Graham]

Sorry............ I'm going to have to 100% disagree..I have a world reknown PhD in chemistry who is into ponds and koi big time...and they produce a whole lot more ammonia for the nitrification cycle than any discus ever could even in soft acid water......along with a local aquarium hobbist who happens to have his Masters in chemistry and works for the university, Along with the best chem whiz I've ever met all agreeing with me and Larry .


The following links will give you the threads on some other boards about this topic with Dr Roddy Conrod, PhD, Dow Chemical; Roark my chem whiz (Jeff Hunan), Engineer in a number of different sciences and Happychem / Stuart McDonald a hobbyist and Masters in Chemistry here in Halifax.........

http://www.koiphen.com/forums/showthread.php?t=43455&page=1&pp=10
http://www.eastcoastaquariumsociety.ca/forum/viewtopic.php?id=7211

Also here is my question to Seachem support and their response..................

''........Is AC capable of de-adsorbing all it's pollutants once it
>has reached it's adsorbing capacity or does it hold onto them
>indefinitely as I've always been taught
================================================== =============================

Your belief is correct. I'm not sure where this misconception
originated. I do not know of any filter media that adsorbs
pollutants to capacity and then leaches them back in. Once they have
adsorbed all that they can your waste will rise again because you
are lacking any open adsorbent media not because they are being
leached out of the media.

Best Regards,
Seachem Tech Support~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Seachem Laboratories, Inc. www.seachem.com 888-SEACHEM
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ch

================================================== ========


While I'm not a chemist, and rely on actual chemists to back up what I've come to know, having had aquariums and fish for the last 46 years and even having bred discus about 30 years ago and having used AC a lot over the years .....Please post the chemical reaction that has aquarium produced acids breaking the chemical bond with the AC.............science please.

Other than that, the notion that AC releases toxins back into the water once they have exhusted that ability is pure myth and there are enough myths in the hobby now with out more being put forward

Regards Graham


Edit I see that your a Prof of Neurobiology so you should have some understanding of basic chemistry......... If they are capable of releasing/ leeching toxins back into the water what are those toxins???


Regards Graham

[mickeyG]

I am not going to post the links or info (way too long) but I have done some research the last 4 or 5 days on the subject. I have read about 20 articles many from well credentialed chemists, and I was wrong.

Most of the experts (all but 1 that I saw) say that after gac has finished adsorbing the offenders (explained the 3 types of adsorbtion in some of the articles), they will not leach back into the water. A few said that there might be very small amounts of a few specific elements that could get into the water but that they were insignificant amounts.

They all mentioned too that they were not sure where the common misconceptions came from, but the fact that they all mentioned this point shows how there are so many opinions from each school of thought.

Michael

[crazie.eddie]

Good information. This should be made into a sticky.

[Alight]

Actually, I do not disagree that AC will likely not leach much of anything back into tank water once it has become exhausted. At least, nothing of significance. I was only making the point that 100% adsorption is theoretically impossible.

I actually believe the negative consequences of AC are:
1) If you are relying on it to remove toxic substances in your tank, you never really know when it is exhausted, and once it is, those toxic substances will build up quickly in your tank

To answer the original question:
"or is it anouther reason why we don't use carbon?"

2) More importantly, as Paul indicated "Carbon is indiscriminate in what it absorbs (adsorbs), ie it absorbs good things as well as bad things, in soft water the trace elements that are essential to all fish will get absorbed quickly and will adversly affect the fish." I believe this is the reason that AC should not be used in a discus tank. Soft water has little of the essential trace elements it to begin with, and AC will take out what little is left--leading to potential sickness. I believe that many of us Discus old-timers have had HITH at least once in our experience, and have had it cured by pulling out AC.

AC does have its uses as a prefilter before RO units to remove chlorine and chloramine that can damage certain types of RO filters, and to remove other nasty compounds before or after RO units that exist in some water supplies. It is also very useful for temporary toxic compounds (such as plastics, sprays, etc.) that happen to get in your tank water, and for removing medicines, once the treatment is finished.

[Graham]

Sorry I must have taken what you wrote the wrong way......But it sure sounded like you thought it could release it's toxins back in....anyway.

As to whether AC use is a good thing or not in a soft water environment, or any aquarium for that matter on a regular basis...that's a whole other discussion and personal experiences will definately play a role here. I have very rarely used AC in the 20 years or more. It has it place on the shelf as another tool when needed for cleaning up the water from whatever, but I would much prefer to do a water change...... I even have a 50 pound bag of it around here somewhere for that day when I might need it

G

[fishmama]

Please forgive me for my simpleton reply...I most certainly agree that it is not intended to replace WC's, but I find AC very effective and helpful. Perhaps the expectations are unreasonable thus resulting in AC being left in circulation too long.

Is it possible that AC left in place after "useful life" may become a favorable environment for secondary growth of undesirable bacteria and/or parasites? Hence, the conclusion that "It must be the carbon."?

Just wondering.

Thanks

[brewmaster15]

Hi Fishmama,

Is it possible that AC left in place after "useful life" may become a favorable environment for secondary growth of undesirable bacteria and/or parasites? Hence, the conclusion that "It must be the carbon."?
At the point the carbon becomes "spent" and no longer capable of chemically removing things from the water, it really becomes nothing More than biological Filtration.. The moment you put it in the water , those same pores at which chemical filtration occur, are excellent places for beneficial bacteria to grow.....so basically it becomes an extension of your biofilter.

Is it useful? It depends on the application....Theres absolutley no doubt that it is excellent for removing things from The tank...but so is a good solid water change.. with added benefit of a wc removing possible parasites and nitrates...something Carbon does not do.,,Additionally the water change has the added benefit of replacing minerals to the water at a proper level.. and decreasing a tanks tendency to drift up in mineral content when the tank only gets topped off after water has evaporated.

Hth,
al

[Timbo]

and decreasing a tanks tendency to drift up in mineral content when the tank only gets topped off after water has evaporated.

an excellent point Al and one i'm sure some folks are not aware of. when water evaporates, only pure water is lost. no minerals, no pollutants, no salt ever leaves via evaporation; the concentration of these elements only goes up until a water change dillutes them (and assuming the change-water is relatively pure, also unlikely unless RO'd)

[fishmama]

Thanks Al!

Excellent info and answered my question...and then some!

Lisa

[crazie.eddie]

I like this thread, becuase I have referred it to several other forums. After doing more research, I found more information...


Con/Myth #4: Old carbon will leach organics back into the water (de-absorption)

This is true in industry, but not in our aquarium. Carbon is widely used in industrial settings to recycle precious metals. Industrial use of carbon involves the capturing of a specific substance at one pH extreme (below 4 or above 10) and then reclaiming the substance by converting to the other pH extreme. If a pH shift of this magnitude occurs in an aquarium, carbon leaching organics back into the water is the least of our worries.
http://www.marineland.com/science/articles/17RevisActCarb.asp

Quoted from this article (http://www.oscarfish.com/cms_view_article.php?aid=606)


De-adsorption

De-adsorption is another phenomenon that is over-stated in the rumor mills about activated carbon. Again, it is an incomplete statement that is commonly used to described the process. It goes, in one fashion or another, as: don't use carbon because once its adsorption sites are full it will release, or de-adsorb, all the stuff it has adsorbed releasing a large amount of pollutants back into the aquarium. The implication in this sentence that activated carbon works something like a capacitor such that once at its maximum adsorption capacity, it instantaneously discharges all the bad things it has adsorbed is wrong. Carbon does de-adsorb, in fact, that ability is exploited for recycling precious metals. However, in a controlled industrial process, the quick release of the target substance is accomplished by switching the pH of the water. The basic process is to capture the target substance at one pH extreme (very acidic or basic) and then reclaim the substance by switching to the other pH extreme. As stated earlier in this article, these pH values are outside the normal range of aquaria. De-adsorption is not a process to be worried about.
Quoted from this Marineland article (http://www.marineland.com/science/articles/17RevisActCarb.asp)

Basically carbon WILL leach (de-adsorb) if brought from an extreme pH to another. As mentioned, if it there was a de-adsorbtion process, then it should be a no concern, becuase the extreme pH shift should be more of a concern. In an industrial situation, this is feasible. In a home aquarium, not a problem at all.