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.
BRAND
|
Average
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Good
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Excellent
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Aq Pharm Black Magic®
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Kent Reef Carbon®
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Boyd Chemi-Pure®
|
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Hagen® Fluval® Carbon
|
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Hydor Prime®
|
█
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Lifegard® Pelletized
|
█
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Marineland Black Diamond®
|
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ROWAcarbon®
|
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|
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Seachem Matrix®
|
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T.L.F. Hydrocarbon®
|
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Warner® Granular
|
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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.