very quick question, carbon - The Planted Tank Forum
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post #1 of 6 (permalink) Old 03-29-2006, 03:07 AM Thread Starter
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very quick question, carbon

Is it OK to leave the activated carbon in my filter for a planted tank? I don't know if it will remove liquid nutrients Seachem Flourish and other stuff from my water. Thanks!
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post #2 of 6 (permalink) Old 03-29-2006, 03:56 AM
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I believe the general consensus is that activated carbon filtration is not desirable in a planted tank. It can remove too many benificial compounds.
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post #3 of 6 (permalink) Old 03-29-2006, 05:45 AM
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Activated carbon is a very useful tool for any aquarium, but you have to understand how it works and how to use it. I like to think of activated carbon as a kitchen sponge.

1. Like a sponge it soaks things into itself and holds it there
2. Like a sponge, once full, whatever was trapped just leaks back out
3. Like a sponge, its nice to have to clean up little mistakes

So carbon acts like a sponge soaking up whatever, good or bad, in the water and trapping it there safely until it is full. What will it trap? I have never been able to obtain a good list, but I will list some of the things I know.

Carbon is GOOD at trapping…

1. Chlorine
2. Pesticides/Herbicides
3. Some heavy metals (Mercury, Gold)
4. Tannins
5. Medications
6. Radon
7. Methane
8. Bleach

Carbon is BAD at trapping…

1. Fluoride
2. Carbon Dioxide
3. Carbon Monoxide
4. Salts/Salt Solutions
5. Nitrates
6. Ammonia
7. Copper
8. Iron (not the kind you use as a fert)

Again, I have never found a full list and not all carbon is made the same or have the same abilities. Some activated carbon sold for aquariums is just plain carbon (charcoal) and will do nothing. Also, the amount most people have is useless. It is recommended to use as much as 1 pound for every 10 gallons. Makes that little packet on your hang-on filter look kinda pointless huh?

So you have your sponge and you have some idea of what it is going to soak up. We can see it can get rid of some real nasty stuff. However, we can also see that it completely ignores some of the most common nasty stuff found in an aquarium. So what good is it?

Back to the sponge. It’s good to have if a mistake is made. Did your wife just spray a spider with insecticide that was hanging out over your tank? Grab the carbon (and some fresh water to do a water change). Worried about harmful gasses under the substrate while moving things around? Grab the carbon. You get the idea.

For regular filtration, it is my opinion that it is a poor choice. It does have a lot of surface area, but it gets full and leaks out whatever it has trapped. Better to use that space with bio media like floss, sponges and rings. I would rather have it on hand for emergencies or when the tank has aged and the water gets to looking a little yellow.
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post #4 of 6 (permalink) Old 03-29-2006, 03:57 PM
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What does Granular Activated Carbon remove?

Asbestos, Chloradane, Chlorine, Chlorination by-products/Trihalomethanes (TTHMs), Mercury, PCB, Toxaphene, Volatile Organic Compounds (VOCs), Odor, Sediments, Turbidity

Q. Will the carbon filter remove all contaminants?
A. No. Activated carbon readily adsorbs (causes to stick to its surface) organic carbon-based compounds, but it does not have an equivalent removal capacity for inorganic compounds such as iron, lime scale, nitrates, hardness minerals (such as calcium and magnesium), or soluble heavy metals like chromium or cadmium.

Perhaps the article (of those here) that best pertains to our concerns comes from Dr. Havonec of Marineland. He disputes some of the 'myths' such as the carbon (once full) leaks out the pollutants back into the aq...and that carbon can be restored by boiling or baking in the oven.
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post #5 of 6 (permalink) Old 03-29-2006, 06:46 PM
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From tests I have seen, I do believe Carbon will leach. Tests were run by monitoring containers of RO water with washed used carbon added.

However, this only happens with carbon that is already full or something is added to the water that weakens the bond between the substance and carbon. In any case, if it comes to this point, leaching really isn’t your problem is it?

I think the myth of reactivating carbon by boiling it came from people whos carbon was not full, but coated by organics. The carbon was fine, just nothing could get to it till the film was removed.

Again, there are many different types and quality of Carbon out there. My view is that it is not going to remove what is commonly in my tank (ammonia, nitrates), but it will remove what shouldn’t be there like pesticides. Running it 24/7 probably wouldn’t hurt anything, but chances are I am just running an extra filter for nothing or taking up room in an existing filter that could have been better used for cheaper and more appropriate bio media.
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post #6 of 6 (permalink) Old 03-29-2006, 07:14 PM
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Originally Posted by Keck
From tests I have seen, I do believe Carbon will leach. Tests were run by monitoring containers of RO water with washed used carbon added.
Please do share these tests with others. If there is a scientific basis to the tests then that would be important to share.

Like said, I think that most people keep carbon on hand, but only use it occasionally. I think people have heard (or are afraid) that carbon removes 'useful / important' compounds from the water. I have not seen any problems with running carbon...although I have not run it in excess. I do occasionally run it to clear up the water...remove excess organics...remove medication. I think for these purposes, it works great.

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