Posted by: joejaworski | May 9, 2008

Does a Reef Tank Need Carbon?


There is no doubt that the biggest selling maintenance product in the aquarium industry is Activated Carbon. This long time filter media started as Bone Charcoal 150 years ago, and it’s been keeping aquarium water sparkling clear ever since.

In the aquarium trade, activated carbon is sold in more products than you think. It is the key ingredient in HOB disposable filter cartridges, and is often blended with ion exchange resins, ammonia removers, and other chemical media that makes up hundreds of aquarium products . And of course, it is sold in bulk or pure form for use in canister filters, mesh bags, and media reactors.

Why do we keep using it? Any veteran freshwater or marine aquarist can tell you that it removes odors, removes color, and makes aquarium water as clear as ice. Despite the beauty of your show tank, no one likes to walk into your living room and get a whiff of that “fishy” smell.

There is a lot of confusion about how activated carbon acts in saltwater, especially when it is used in reef aquariums. Here, aquarists are constantly pushing for a more natural filtration approach. But it bugs the hell out of me when I read all the misinformation on the Internet and even on carbon product labels. They preach to use carbon sparingly, like one day or three days a month, or don’t use it all. Folks, Activated Carbon is non-toxic. It cannot be overdosed. It will not remove all the salts and trace elements and turn your tank into some incomplete blend of synthetic seawater.

We all need to realize that our reef and fish-only aquariums are NOT miniature slices of the ocean. They may look that way, but bio-chemically they are an ecosystem that is always on the verge of collapse. Activated Carbon’s job is to remove metabolic wastes, or more commonly called organics. You can employ the deepest sand bed or the largest calcium reactor or a humongous circulation pump, but none of these things will have any effect on organics.

When it comes to organics, the world’s oceans maintain a perfect balance of metabolic waste removal through a series of natural recycling systems. Both the volume of water and the immense surface area provides a home for tens of thousands of species of macro and micro organisms that process these wastes. In the home aquarium, just a small fraction of these organisms can survive. Coupled with an extremely high specimen to water ratio, organics tend to accumulate in closed systems, and can reach concentrations orders of magnitude beyond natural ocean levels. Even with aggressive water changes, these organics can never be diluted enough to mimic the natural levels where our livestock has lived for thousands of years.

Don’t confuse organics with ammonia, nitrites, or nitrates. The bacteria responsible for breaking down these nutrients naturally thrive in all aquariums. Most tanks are nutrient rich and provide lots of food for these bacteria to thrive. Organics on the other hand, consists of complex metabolic compounds including phenols, organic acids, proteins, fats, carbohydrates, and hormones. To break these down, we don’t (and can’t) grow the right bacteria in our aquariums. In fact, detritus on the gravel surface and in the bottom of the sump are organic compounds that have reached such high concentrations that they fall out of solution. These particles remain inert as long as pH, oxygen, and ORP levels stay constant. Any wild swings or disruptions will trigger detritus particles to release these pollutants back into solution, causing an avalanche effect which will fuel a tank crash like there’s no tomorrow.

Where Do Organics Come From?

Creation of organics is a natural process of fish and invertebrate metabolism. It has little to do with the amount of food added to the tank. Reef tanks are especially vulnerable to organics, since corals and invertebrates produce a lot more organics than fish. Coral “slime” is nearly 100% pure organics. When you are mounting a coral or moving things around, copious amounts of sliming results. This slime is torn apart by powerheads, oozes through mechanical filters, and finally winds up being dissolved in the aquarium water. By contrast, coral slime in the ocean is quickly washed away perhaps hundreds of meters away from the coral. It is then consumed whole by other invertebrates or fish or quickly broken down by specialized bacteria and used by plankton as food. Everything is recycled in the ocean. In the aquarium, it has to be removed.

Why Organics Are Bad

While only a few of the organic compounds are directly toxic to marine livestock, they can stimulate the growth of heterotrophic bacteria which robs your tank of oxygen. These bacteria also create carbon dioxide. The result is lower pH and low ORP, which creates ideal conditions for nuisance algae to thrive. Organics can quickly tint aquarium water to a yellow color which greatly blocks blue spectrum light penetration (actinic 420nm). High levels of organics can also tax a protein skimmer to the point where nitrates and phosphate removal becomes minimal.

No one knows for sure the total make up of organic compounds in the marine aquarium and what specific effects they have on different organisms. It had been observed that aquariums with high organic levels experience more fish and coral diseases. There is now firm evidence that organics stunt fish growth. The old mystery of how a fish will grow only as large as its container has been solved. It has nothing to do with the volume of water or the size of the tank- organics accumulation is the culprit.

At moderate organic levels, corals and invertebrates tend to close or cease reproduction. Some researchers believe that there is a direct relationship between high levels of organics and dense populations of disease organisms. The reduction of naturally occurring organics ultimately leads to improved water quality and healthier specimens. Activated Carbon is the most effective and easiest method of removing organics from aquariums.

How to Tell if Your Organics Levels are High

The tell tale signs of high organics in marine aquariums include (1) Persistent hair algae problems despite low nutrient levels, (2) Some foaming in the sump or in the corners of the tank, (3) An oily film or cloudy layer on the water surface where even a tank overflow can’t seem to get rid of all of it, and (4) small growths of Cyanobacteria spotting on rocks and the gravel.

How Activated Carbon Works

Activated carbon is a unique product that starts out as nut shells, wood, or coal. It is pyrolysed in a 750°C oven which cracks the material and creates millions of micro pores on the surface and though the interior of each grain. The surface area of these pores are immense. One gram of granular activated carbon has 5,300 square feet of surface area. By comparison, a tennis court is 2,800 square feet. It is not only the large surface area of carbon that attracts organics, but there is an electrical charge involved that draws organics to the carbon.

Choosing Activated Carbon

In the aquarium trade, bulk activated carbon is sold in granular and extruded forms. Extruded products appear as pellets and spheres. These carbons are more rugged and can take tumbling in media reactors without breaking apart. They also tend to have less dust. However, extruded carbons have less surface area than granular carbons, so more product will be needed to achieve the same results. Granular carbons are softer and are more dusty. Dust level has nothing to do with the quality or effectiveness of carbon.

There are lots of brands of activated carbons to choose from. The quality ranges from downright detrimental to excellent. Avoid any product that uses the term “charcoal” or “char” in its name. These products are not activated and are limited to removing heavy metals and odors. There are ineffective against organics. They also contain calcium phosphates- which act as a nutrient for algae growth.

Activated Carbon has gotten a reputation of adding or leaching phosphates back into the water. This is only partially true. Activated Carbon can be made in two ways, either by Physical Activation or Chemical Activation. Physical activation used CO2, oxygen, or steam, and contains no phosphates. Chemical activation uses phosphoric acid and zinc for activation. If you buy the latter, then adding carbon will also add phosphates to your water. You are better off not using carbon at all then using a phosphate washed product.

Here’s a guide on what to look for when buying activated carbon:

Look on the product label for information about the carbon. If the label talks about the carbon process of using steam, oxygen, or carbon dioxide, then it is truly phosphate-free and won’t leach phosphates into the water. Some carbons are simple marked “Phosphate-Free” which indicates a steam activated process. If the label does not mention phosphates, doesn’t tout the activation process, or requires rinsing to minimize phosphates, it is likely a low grade phosphor-washed carbon that should be avoided.

If you use your carbon in a media reactor or tumbler, buy an extruded or pelletized carbon. It won’t break apart when the grains bang into each other. For use in canister filters or mesh bags, use granular carbon. It will give you more surface area- albeit at the cost of being softer and more fragile.

Ash is an inorganic material that is left behind after the activation process. Look for carbon that is marked as low ash content or one that states “Does not affect PH”. High ash content can cause a significant rise in PH when first placed in the aquarium. This can cause undue stress on the livestock. I have personally seen pH values climb within minutes from 8.0 to 9.5 pH with some carbons. All carbons contain some ash and a thorough rinsing in fresh water will remove most of it.

Quality brands of activated carbon will feature other parameters, such as Iodine Number below 600, Molasses Number above 400, or listing pore size in Angstroms. These are all signs of a quality manufacturer that has nothing to hide, and is offering a superb product.

Marineland Black Diamond

ROWA Carbon  █

BRAND Average Good Excellent
API Activated Carbon
Kent Reef Carbon
Boyd Chemi-Pure
RedSea Reef-Spec
Hydor Prime
Marineland Black Diamond
AquaMaxx Carbon One
Seachem Matrix
TLF Hydrocarbon
Cobalt Carbon


How To use Activated Carbon

For ongoing maintenance, I recommend 1 cup per 60 gallons of water. This is a bit higher than most suggestions, but using more carbon works faster and lasts longer. Double this amount for tanks with obvious signs of high organics or first time carbon use in poorly maintained tanks.

Filter the water mechanically before it reaches the carbon. Particles greater than 100 microns in size will take a toll on the life of the carbon.

Despite popular belief, carbon does not need to be placed in a canister filter or a compartment where all tank water passes through it. Dropping a mesh bag full of carbon into the sump works fine. This is because carbon works by electrically attracting particles- it is not an inert mechanical filter. Studies have shown that bags of carbon in a sump with moderate flow removes substantial quantities of organic pollutants, medications, and heavy metals. Actual performance depends on the flowability of the bag material. It is most effective if you use a media bag with the largest possible hole sizes but small enough where the carbon cannot escape.

For the average marine fish aquarium, carbon will last 6 weeks. Reef tanks produce more organics than fish-only tanks, so 4-6 weeks is a workable limit. If the water is not mechanically filtered or the aquarium shows signs of nuisance algae, you will need to adjust the useful life or increase the amount of carbon.

There is no effective way for the aquarist to either recharge carbon or measure its rate of exhaustion. I have experimented with the Salifert Organics Test Kit to measure carbon life, but I was unsuccessful because the range of the test kit would not allow me to measure steady declines over time. Don’t re-use carbon or try to clean it. Recharging carbon requires a specialized high temperature/low oxygen oven that would be prohibitively expensive at this small scale. The best solution is to replace the carbon at 4 to 6 week intervals.

Activated Carbon Myths and Misconceptions

Carbon removes trace elements– Carbon has a greater affinity for organics than trace metals, but it will remove some trace elements. On the other hand, both protein skimming and natural consumption of trace elements by tank specimens will remove significantly more trace elements than carbon. Aquarists concerned about depleted trace elements should be using a trace mineral additive- whether or not carbon is used. Two excellent products for this are the Sera Strontium Complex and the Seachem Reef Trace products.

Carbon will leach organics back into the water False. Once all the carbon pores are saturated, bacteria slime and detritus will accumulate on the carbon grains, turning it into a weak biological filter with the organics locked in the deeper layers.

Carbon should be used only a few days a month False. This myth was likely started by activated carbon’s ability to remove yellow tinting and odor from the aquarium within the first 48 hours of application (or perhaps manufacturers who want to sell you more carbon). The higher concentrations of organics are colorless and odorless and require more contact time for removal. Another complication of part-time carbon use is storage and reuse. Once the carbon is removed from the aquarium it will continue removing contaminants from the air. Placing the damp carbon in a sealed plastic bag doesn’t work either, as the damp carbon becomes exhausted servicing die off in the stagnant aquarium water stuck to the grains.

Spilled carbon causes harm to the aquarium False. Carbon granules that are accidentally spilled into the aquarium will quickly become saturated with bacteria slime, having the same biological effects as a grain of gravel. It may look ugly, but it is totally harmless.

As we have seen, the use of Activated Carbon is an important part of maintaining a healthy marine or reef aquarium. It is the only filtering media that can remove substantial amounts of metabolic wastes (organics), which accumulate over time and can prevent secondary water quality and health problems in specimens. Because of the phosphate issue in lower quality products, it is better to spend a little more on a quality carbon than use any carbon at all.



Disclaimer: I am not affiliated with any brands or product names mentioned on this web site. I don’t receive any commissions or referral fees for any brands listed. Be wise- if you read a blog and see “amzn” links to products the author is getting paid when you click on it, so any info may be biased.

Copyright (c)2018 Joe Jaworski. Reproduction by any means is strictly prohibited without permission.



  1. Hello there,

    That was very informative and quite awesome to read. Thanks for taking the time to express your opinion. I was wondering what you thought of PURIGEN? I see you have chemipure on the list, but I am really interested in your opinion of Purigen.

    Kind regards,

  2. Purigen claims to have similar pore structure and electrical affinity for organics as carbon. I have tried it in the past and does work. Though I have not compared it side by side with carbon for effectiveness.

  3. did you ever heard about Faunamarin carbon? I heard it 1 of the best
    I’d like to know if you have any information

  4. I haven’t used or tested Faunamarin carbon. I do know a lot of people who are happy with their amino complex product.

  5. NICE write up,

  6. Well, I know I’m going to change my LFS after reading some of your articles. Too much to discuss and my lunch break is over. I have lots of questions …In other words I’ve been deceived. I have a 75 gallon Reef tank for about a year and have problem with nitrates and not to sure about carbon… Now that a read you article some things a really clear to me… Thank for the informative info…
    Jose Pellot

  7. Joe,
    Could you tell us more about your findings with Purigen? I’ve been using it in tandem with carbon for some time now. I’m concerned about Purigen adsorbing my trace elements. Would you run both of these at the same time? Also, the method for recharging Purigen; although easy, concerns me somewhat because of the chlorine. After recharging, I allow my Purigen to sit and dry (sometimes for weeks). The directions on the package says that some chlorine removers shouldn’t be used as it reduces the effacacy of the Purigen. Any comments would be greatly appreciated. Thanks. Tom

    • Buy yourself some Sodium Thiosulfate. I use this all the time to neutralize chlorine when cleaning my equipment and tanks. It would be equally effective on purigen. Places like Aquatic Ecosystems sells it. Throw a few grains in the water and the chlorine smell will be gone in minutes. Then, rinse with freshwater. This is the number one ingredient in commercial chlorine removers.

  8. Do you have any opinions on the carbon products offered from Bulk Reef Supply? ROX carbon, etc?

    I also use Purigen, carbon, and Phosban – is this all necessary or does carbon do it all?

  9. Phosban and other phosphate removal media has a higher removal rate of phosphate than carbon. If phosphate readings are high, then these products can be used in addition to carbon.

    Sorry, I have no first-hand experience with either ROX carbon or Purigen.

  10. Another great article! And l’ve learnt so much more reading articles (most are real eye opener) in your webblog than other marine books and forums!

    Definitely recommending all my reefer friends to read yr blog.


  11. Hi Joe,

    I am producing an article on activated carbon for the website I came across your image above on Google image search and would love to use it in my article. May I?



  12. No problem, Mike.

  13. Joe,
    Thanks another grt article!
    When you mention Hagen Fluval carbon in your chart, are you referring to the Fluval carbon or the Fluval Opti-carb, which is more like chemi-pure?

  14. Thanks for the best answer I’be seen in 45 mins of googling.

  15. I have heard that activated carbon is a suspect in cases of Head and Lateral Line Erosion. What is your thoughts on this. Thanks

  16. I’ve never been able to find any scientific studies that pinpoint the cause of HLLE. There is anectodal evidence that lots of things cause it, so I’m not surprised that carbon is on the list. No one has ever documented observing the disease in the wild, so it may very well be an autoimmune problem related to stress.

    Personally, I don’t see how carbon can cause stress unless a low grade variety is used to raise pH too quickly.

  17. […] Her er en god artikel som omhandler brugen af aktivt kul. […]

  18. How is activated carbon different from Charcoal, I met a LFS lately and was told that he uses normal charcoal and it performs very similar to activated carbon for very little of their price. (put aside any of the igitiation additives added to aid burning)

    He is talking about the wood pieces charcoal not the man-made pellets.

    • Doing the same, the Charcoal after the braai. I wach it and use it in my filters and sump. I am using quite a lot Buget + (I have a 200gal tank) I rede a article that one is to use only 2tb spoons per gallon so maybe I am overdoing it?? But it works and hade no bad effects the past years.

  19. Joe,
    What is your opinion of catalytic carbon, is it safe to use in the reef aquarium? (Centaur for example)

    I really enjoyed the article, great analysis.

  20. Calgon states in their literature that it can be used for aquarium filtration. However, I believe the largest grain size available is a 12×40 mesh, which is about the size of sugar granules. Some form of custom housing would be needed to prevent it from escaping into the aquarium.

    • Thanks for the quick response, my main concern was whether it contained something extra that would be bad for the aquarium.

  21. I had the same problem with my yellow tang with Lateral Line Erosion and my friend suggest me taking the carbon from the media reactor for a week and in day the yellow tang was getting better since then I haven’t use carbon. now I will try it again hopefully nothing happens

  22. As an anecdotal response regarding activated carbon and HLLE, I frequently buy “scratch and dent” tangs from my LFS.. They are usually quite healthy, except for having HLLE from the POI.. And I’ve nursed every one of them back to full coloration while in a tank that is running carbon in a canister filter.. HLLE, in my experience, is more of an issue of malnutrition while the fish are in transit.. And possibly a psychological effect of being removed from a reef, and kept in a tiny plastic cage for (sometimes) weeks before being put into our systems.. On another note, a fantastic article!

    • Aaron,
      I would be interested in an email from you detailing your HLLE treatments. My Yellow Tang is starting to develop some erosion above and behind the eyes. I use a varied diet mixing/rotating Marine flakes, Hikari Extreme Seaweed Pellets and Algae Wafers, a variety of Hikari frozen shimp (Brine, Mysis, Spirulina), Hikari Frozen Bloodworms, Arctic Pod Feast, various dried seaweeds, and broccoli. I began soaking in Boyd’s Vita-Chem and Selcon soon after noticing the ailment. All other fish (2 Banggia Cardinals, 1 Powder Brown Tang, 1 Yellow Tailed Damsel, 1 Neon Dottyback, 1 Coral Beauty, snails, crabs, 2 shrimp, and 2 stars) appear normal and healthy. 125 gal tank with a Fluval FX-6 and 20-25 gal water changes @ every 10 days. Any advice would be appreciated.


  23. I just found this very well written and informative article. Thank you very much.

  24. […] Re: Questions about BioCube 29?? Carbon is your full-time friend Carbon works […]

  25. hi joe
    can i please use some of the artical to explain the way carbon works on a uk forum i mod on ,pete

  26. Sure, that will be fine.

  27. thank you joe ,regards pete

  28. […] […]

  29. have u any thoughts on Activated Tri Base Pelletized Carbon ??

  30. […] […]

  31. […] […]

  32. Good

  33. very informative and good read. Useful information for all slatwater enthusiasts! Thank you

  34. Awesome read. Thanks for taking the time out of your day for this info.

  35. […] […]

  36. […] […]

  37. Of all the forums and sites i have been on your information has proved the best and easiest to understand, i have always been confused when reading about lighting. Your article made perfect sense, thanks. Will chomp my way through all your articles now.

  38. I live in Stilbay south Africa. We are a few guys here that have marine tanks, we catch our own fish and had no problem the last 7years since my tank in up and running. We only use burntout wood in our filteres and sump . Water is nice and clean with no odour.

    Much cheaper and doing the same thing.



  39. Nice article and is currently doing the rounds on various forums :o). You mention that 1 cup per 60 gallons is recommended. Can I ask what size cup you mean, or maybe even a weight? Am I also right in assuming US gallons?


  40. 1 cup ~ 240ml = 60 US gallons (~227 l)

    • Excellent, thank you for your very quick answer.

  41. Excellent read Joe! Thanks. I use carbon full time, and your article helps put my mind at ease regarding all the misconceptions. Do you have any thoughts on the latest info regarding activated carbon and HLLE?

  42. […] […]

  43. […] […]

  44. Great article! Learnd a lot from it. A quick question:

    You mentioned “High levels of organics can also tax a protein skimmer to the point where nitrates and phosphate removal becomes minimal”. However, in my impression, skimmer is used to extract DOC, can skimmer remove such small molecures as nitrate and phosphate?

  45. Awesome write up.

  46. […] […]

  47. Wow! Great article! Well written easy to understand very informative. After reading many articles inreference to reefkeeping what I liked most about this article is I came away with a complete understanding of a complex subject!
    Bruce silver

  48. Great article thanks for taking the time to write and post it. Couldn’t decide if I wanted to use a carbon reactor in my tank or not, I finally got my answer, not to time to do some shopping.

  49. i threw away my charcoal on the advice of my local shop as he said it was bad for the system i was setting up.i am new to marine but have kept tropical for about 20yrs and have sworn by carbon in my filters the whole time .your article was well worded and easy to im confused as to wether or not to get more carbon or stick with what i have now.any other little gems you may have would be most welcome.

  50. I completely agree!

    However obviously creating a well balanced self cleaning ecosystem is best (by self cleaning I mean, water change by siphoning the bottom once a year so no over development of certain things…it is indeed a closed system).

    For my freshwater I use only live plants, have tons of fish, but crystal clear water…no filters. My saltwater has 2 different macro algaes, clear water… no filters. But finding your balance is hard, and supplementing with carbon has always been my thing when it is needed.

  51. What are your thoughts on using carbon and biopellets together

  52. […] […]

  53. Loved the article and was curious what you think of Dr g’s carbon. On the back it says best carbon money can buy

  54. What is ur take on protein skimmers vs carbon in a reef tank?

  55. Dear Joe
    Not into marine…yet.
    Just trying to help a friend solving the yellow tint in her marine tank…
    Came across your so informative and usefull article…!
    Thanxzzz many!!!

    Best fishes from an feshwater aquarium in Namibia, Gert

    P.S. Do you ever heard about the Anoxic filter (for koi ponds) from Dr. Kevin Novak?
    Pretty much the same effect with the highly pourous cat litter and magnetic activity of laterite…all in a relatively anoxic area…

  56. Hello, Activated Carbon in Reef Aquariums back in the day was always a No No. But nowadays some say it’s ok & a must. Although I found your article with much information on other things, I still have not seen any provided proof to your claim that Carbon does not remove Trace Elements other than you just saying it doesn’t. So my question to you, Do you have any legitimate and actual proof, or know of anyone who has actually scientifically tested this issue in a lab or any kind of hard facts to back up your claim? Because so far, all I’m seeing is he said, she said so far. Now before you go thinking I’m just a procrastinator, or just out to troll your article, I will admit that I use Chemi-Pure Elite in my 125 gallon reef. Which is easy to see if you look at it that it is indeed activated carbon mixed with Ion exchange resins & Ferrite Oxide. But no where on their bottle does it mention Activated Carbon. This too is misleading to the Reef Aquarist.

    Also, you state that Organic Matter has nothing to do with the amount of food.

    Quote: Creation of organics is a natural process of fish and invertebrate metabolism. It has little to do with the amount of food added to the tank.

    If this breakdown of these components such as left over food, is not considered Organic Matter, then what is the breakdown of left over food considered? Waste is Waste, whether it’s metabolic or not. left over food is broken down either way. Is this not considered waste as well? I have found over the last 30 years of my aquarium experience that if one’s water is smelling rotten, then he or she is not doing regular water changes, is over feeding the tank, not cleaning the filters, or something has died and is rotting somewhere.

    Also, Skimmers are indeed organic waste removers and if one does not have one, then yes, carbon or some sort of plant system must be implemented to consume that Organic Matter such as culerpa, chaeto, or mangroves and the such. IMHO, running a reef without a skimmer is asking for trouble without the other disposal methods. So does this mean the Reef Aquarist is forced to use Activated Carbon when the real problem lies to lack of Maintenance? And also if forced to use Carbon, at risk for removal of Trace Elements as well? But as for Activated Carbon, you first state that your tired of hearing it removes Trace Elements,

    Quote: But it bugs the hell out of me when I read all the misinformation on the Internet and even on carbon product labels. They preach to use carbon sparingly, like one day or three days a month, or don’t use it all. Folks, Activated Carbon is non-toxic. It cannot be overdosed. It will not remove all the salts and trace elements and turn your tank into some incomplete blend of synthetic seawater.

    then in the middle of your article you come out and I quote:

    Quote: ► Carbon removes trace elements- Carbon has a greater affinity for organics than trace metals, but it will remove some trace elements. On the other hand, both protein skimming and natural consumption of trace elements by tank specimens will remove significantly more trace elements than carbon. Aquarists concerned about depleted trace elements should be using a trace mineral additive- whether or not carbon is used. Two excellent products for this are the Sera Strontium Complex and the Seachem Reef Trace products.

    Although I do agree that skimming will remove many things, medicines, calcium, and I agree with you (Some Trace Elements), You still contradict yourself.

    Let’s face it, Activated Carbon either removes Trace Elements or it does not. Which is it? And again, do you have any hard testing facts or laboratory proof that it does not remove Trace Elements? If so, can you provide a link to your findings? Thank you for your time.

    An Avid Reef Aquarist, 30 yrs.
    Somewhere Near Chicago, IL

  57. Have you ever seen fish die from high levels of organics? I recently lost all of my fish and all of my water parameters were in a acceptable range. I’m wondering if my oxygen levels plummeted as a result of high organics. Algae was growing wild with Nitrates and Phosphates at 0 ppm. According to your recommended carbon dosing I was under dosing big time. By the way this an incredible article on the topic.

  58. Time to update this a bit.. running activated carbon constantly actually does remove trace elements according to this article and recent research relating to fish health.

  59. One of the best articles I’ve read on carbon. I’ve had freshwater tanks for 35 years and now have 2 Nano Reef Tanks. Activated Carbon has always done well for me and it is working awesome for my 4 Gallon Nano reef and my 24 Gallon Nanocube!

  60. If you’re worried about trace elements being removed, add only enough carbon so that you’re replacing every week. When it it’s time to replace, pull out your carbon, dose with trace elements and leave for half the day before adding fresh carbon. I’ve had to add a lot of carbon to get rid of organics and I haven’t had any issues.

  61. Carbon does harm some torch corals. At least in my tank.

  62. What a great explication of a complicated process! I started using activated bituminous charcoal. My protien skimmer skimmate production then dropped by at least half. As the air pump was nearly 3 years old, I disassembled and cleaned it, thinking it was obstructed. Now I realize that the charcoal has been clearing large organic molecules and leaving less for the skimmer to remove! My tank was very healthy before (mostly soft corals and fish, including several fish that live off the live rock and are never directly fed by me), Now the water is a bit clearer, but (I’m betting) a lot healthier. Thanks for your excellent contribution to this magnificent hobby.

  63. I’ve been running carbon for the past few days and now my Ca is as low as 320 even 12 hours after a water change. Mg went down by 100ppm over night. I didn’t have that problem before so yes carbon sucks out the live of your tank. It’s only logical as carbon picks up everything that’s in the water. That’s why you use it in your RO/DI unit. It removes everything. And you can overdose it. Talk to the people whose tangs developed HLLE or whose corals bleached from a rapid depletion of nutrients.

    • Well on the flip-side, Eric Borneman once stated that if he had to remove either skimmer or carbon from his tank, he’d remove the skimmer.

      So if carbon doesn’t work for you, by all means remove it.

  64. Hi there,

    When I first opened this article, I was amazed that someone could write so much about activated carbon. As I read through, I had more and more questions, and you managed to answer every single question by the end. As a new reefer, I am very grateful that you took the time to write this whole article (including the chart of average, good, and excellent brands), and I definitely plan to follow your advice. Your knowledge and ability to teach is much appreciated. Thank you very much!


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