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Educate me about carbon! : )


tithra

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So, I have totally gone with what I have learned here regarding carbon and that it is not necessary in an aquarium and can leach toxins back into the water if not changed out regularly.

But I would like to have a better understanding of carbon

- what is it supposed to do in an aquarium exactly? (what exactly does it remove?)

- does it truly "get full" and leach out what it has collected over time or does it just get full and stop working?

It seems like so many people use carbon, and while I have not interest in using it (I don't need another aquarium expense lol), I would like to have a better understanding of it (I think it is dangerous not to question what you have learned ;) )

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Here is a really good article on carbon

http://www.thetropicaltank.co.uk/carbon.htm

I use it most of the time in one of my tanks and not the other, since for some reason, the water gets a little cloudy if carbon is not there. As you will see in the article, it actually takes some effort (like a very drastic pH swing) to force the carbon to release back the things it has adsorbed.

However, I think that carbon can be a bad place for bacteria like Aeromonas to grow.

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Carbon has a HUGE surface area because it's really porous. It also chemically binds to a lot of substances. So that means it can bind a lot of chemicals, etc. which is why we use it to remove medications.

The problem is that once the carbon is 'full' (all the binding sites are taken) it can start to reverse the process and release the chemical compounds back into the water, so if you use it you need to be sure to change it fairly frequently, just rinsing won't do the job.

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Carbon has a HUGE surface area because it's really porous. It also chemically binds to a lot of substances. So that means it can bind a lot of chemicals, etc. which is why we use it to remove medications.

The problem is that once the carbon is 'full' (all the binding sites are taken) it can start to reverse the process and release the chemical compounds back into the water, so if you use it you need to be sure to change it fairly frequently, just rinsing won't do the job.

I am really wondering if the part about it releasing the chemical compounds is true or not... there seems to be a lot of competing information out there on this. For example, the article that Alex posted said that there needs to be an extreme condition for this to actually happen and that it would be rare in a typical aquarium, but then so many people say that it does leach stuff back out when it is full. This seems like something that could easily be studied and determined, there must be a definitive answer on this :D

Edited by tithra
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There is a definitive answer on this, and that is: under normal conditions, carbon won't readily release this back into the water. One way to do is that you have to quickly reverse the pH of the water (going from basic to acidic or vice versa.) Remember your chemistry. The adsorption is a chemical process, and in order for it to be de-adsorbed, you have to chemically sever these bonds. Here are two more links. The second one is even better.

http://www.cichlid-forum.com/articles/marineland_carbon.php

http://science.howstuffworks.com/environmental/energy/question209.htm

The other thing to keep in mind is that we use carbon filtration in a lot of things, including use in drinking water filtration. If it is that easy to the nasty bound chemicals to be released, there would be a totally unsafe thing to do, as many very careless people who use these filtration systems will be getting sick left and right.

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Here's a really good sheet about the chemistry of it all :)

http://www.cee.vt.edu/ewr/environmental/teach/wtprimer/carbon/sketcarb.html

The trouble comes when the carbon reaches the 'breakpoint' where every single part of its binding surface is taken. At this point it will stop filtering and potentially release the compound back, depending on how highly it is concentrated in the water. If the concentration's not high, it probably won't release it, but it will physically break down because carbon is relatively delicate - and that will also potentially release compounds back.

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:rofl I avoided chemistry like the plague Alex! My first brush with chemistry was in college in a geology class lol.

Okay, thank you again for the articles. I have done some research online as well now and it does seem that this carbon leeching toxins back into the water is mostly a myth, except under the extreme circumstances you point out.

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Thank you for the article Chrissy. That is an interesting point about it physically beginning to break down and the potential for it to release at that point. I wonder how long that process would take.

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but it's also very unhealthy to keep it in the filter for a long time like some people do. :(

This IS something to be concerned about. Certain activated carbons will release phosphates into the water. Morever, as carbon binds to all sorts of chemicals, it eventually becomes a very good breeding ground for pathogens, including Aeromonas.

I don't mind using it, but I am very happy not to have to use it in one of my tanks :)

Edit: tithra, the breakpoint in these carbon products is 1-2 months. You should see them telling you in the directions :)

Edited by dnalex
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Thank you for the article Chrissy. That is an interesting point about it physically beginning to break down and the potential for it to release at that point. I wonder how long that process would take.

I think it would depend on how small the pieces were and how much physical wear and tear they were getting (being moved around in the filter during cleaning, etc).

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I just want to add if not well rinsed carbon can release pretty irrititating bits into the tank. There are varying opinions about whether or not this can cause ulcers. I do on occasion use carbon because there is a lot of pollution in our air, but I am pretty religious about rinsing well and changing it monthly.

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I just want to add if not well rinsed carbon can release pretty irrititating bits into the tank. There are varying opinions about whether or not this can cause ulcers. I do on occasion use carbon because there is a lot of pollution in our air, but I am pretty religious about rinsing well and changing it monthly.

This is a great point too, although this has to do more with how the people work with it. I remember when I still used the cartridges for my filter, I had to rinse the new ones really well in order to get all the carbon dust out. That part always really bothered me.

Other than that, I need to go up there and LIKE pretty much every post now. This topic was very educational, thanks guys! (And I wasn't even the one asking here :D )

EDIT: I just read the first article and came across this here: "It should help to remove pheromones given off by fish that can inhibit their growth."

So carbon - in theory - can help prevent stunting? Now I am not saying that this is the wonder solution and would prevent stunting if you have 5 gallons full with a dozen single tails. This is more something that I am wondering about in my currently somewhat overstocked tanks. (like 7 in 55) I'd still want to perform my weekly total of 160% water changes as before, but I wonder if adding carbon would be additionally beneficial.

Edited by Oerba Yun Fang
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