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CARBON DOSING
AN EFFECTIVE MEANS
OF
NITRATE AND PHOSPHATE
CONTROL
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By James Gasta
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One of the newer trends in lowering
dissolved waste in marine aquaria is by carbon dosing. Carbon
dosing is an effective means of increasing heterotrophic bacteria by a
controlled feeding of a carbon source.
How Does It
Work?
Increasing the beneficial
heterotrophic bacteria (bacteria that feed on dissolved nutrients such
as nitrates and phosphates) population in the aquarium water by dosing
a carbon source will increase these bacterial colonies to a level that
will effectively remove nitrates and phosphates from the water.
Large colonies of beneficial bacteria can only exist with a controlled
feeding of an organic carbon compound at specific intervals. This
process can take three to five weeks, depending on the nutrient load
and carbon source used. Colony densities can be adjusted by
controlling the amount of the carbon sourced dosed. When the
bacterial colony is established, nitrates and phosphates can be
controlled to very low levels or zero if desired. Natural sea
water contains 28ppm of carbon and may be present at this level in some
of the better brands of salt mixes. This may be the reason in
part why aquarists who do weekly water changes experience healthier and
algae free systems. Carbon dosing is basically a means by which
we dose organic carbon compounds. These compounds include
ethanol, acetic acid, sugars, bio-polymer pellets, and ascorbic
acid. When using a powder or liquid form of carbon dosing, it is
important not to miss a dose as doing so will reduce the bacterial
colony and will cause a set-back in developing the process.
Overdosing can also cause a dramatic drop in oxygen by an over
abundance of bacteria which consume oxygen and can have a detrimental
effect on the livestock in your aquarium. It will also cause a
large bacterial bloom resulting in cloudy water. Should this
happen, stop dosing immediately until the water clears. At this
point you will be basically starting over so do follow the
manufacturer’s instructions to the letter. Carbon dosing is
beneficial in systems with a high bio-load where efficient protein
skimming and frequent water changes are not enough to keep nitrates and
phosphates at desirable levels. Large systems or systems with a
light bio-load that are efficiently skimmed will likely not benefit by
this means if nitrates are already at acceptable
levels.
Do I Need Additional Equipment to Dose
Carbon
Depending on the dosing
method you choose, you may need nothing more than a syringe or
measuring spoon. The use of bio-polymer pellets will necessitate
the use of a fluidized up flow reactor, flow control valve, and
pump. Regardless of the dosing method you choose, an absolute
must is a good efficient protein skimmer rated for at least 1.5 times
the volume of your tank. Once the bacterial colony is
established, they will consume nutrients and these nutrient laden
bacteria will slough off or shear away from the biofilm the colonies
produce. These bacteria will need to be exported by a protein
skimmer although the metabolism of these bacteria will also export some
waste as nitrogen gas.
Types of Carbon
Compounds
For this article I will concentrate on the
most commonly used products for this purpose. Before dosing any
carbon source, test your system’s NO3 and PO4 levels. Do not
begin dosing without knowing this as this will be important later on to
determine a maintenance dose level. Good test kits are
recommended and look for kits that are capable of accurately measuring
low levels.
Vodka
Carbon dosing initially started out with the
use of Vodka as a carbon source. Why Vodka you ask? Since
Vodka contains no additives and contains only water and
the organic compound ethanol, it is much safer to use than other
spirits which do contain additives that could have a negative effect on
the system. Vodka is also one of the more economical means of
dosing providing you do not dose yourself with it while dosing the
aquarium. No need to buy high grade Vodka, the cheapest brand of
80 proof (40% alcohol) Vodka will work just fine. The following dosing
procedure is recommended when using Vodka.
First three days – 0.1ml per 25 gallons of
actual aquarium water.
Days four through seven –
0.2ml
Each subsequent week add an additional 0.5ml
of vodka
After week two you should see a reduction of
nutrients. If no decrease is noted by your test results, increase
the daily dose by another 0.5ml.
Once your NO3 and NO4 drop to an undectable
or a level you desire, decrease the daily dose by one half. It is
at this point where you will need to determine a maintenance
dose. If nitrates and phosphates rise, increase the daily dose by
0.2ml. If the levels remain undectable, decrease the daily dose
by 0.2ml. For reef systems we are looking for nitrate levels in
the 5-10ppm range as some invertebrates such as clams do benefit by
some nitrates present in the system.
Bio-polymer
Pellets
Two Little Fishies NPX
Bioplastic Pellets
An easier method of
carbon dosing is by using bio-polymer pellets, sometimes called solid
Vodka, solid polymers, and bioplastics. These pellets or beads
are made from petroleum based polymers. The heterotrophic bacteria live
and feed on these pellets and in the process uptake dissolved nutrients
from the water thus lowering nitrate and phosphate levels. The
instructions that come with the pellets should state the amount
required for a given tank size. This method of dosing requires a
fluidized up flow reactor, pump, and flow control valve.
Depending on the reactor chosen, you may have to purchase screens
fine enough to prevent the pellets from escaping the reactor. Water
flow is adjusted with the flow control so all the pellets tumble within
the reactor. This is important as too little water flow will
cause the pellets to clump. The size of pump will be dependent on the
size of the reactor, length of tubing from pump to reactor, and the
amount of pellets required.
Reactors made for this application generally
state the size of pump needed. It’s much better to have too
much pump as you can always throttle the flow back with the flow
control. This method is much easier compared to the required daily
dosing of Vodka. The pellets will slowly dissolve in time and
will need replenishment to maintain the desired bacteria
population. When the reactor is filled the first time with the
recommended amount of pellets, it is a good idea to make a mark on the
reactor showing the pellet level. After a few months pass you can
shut down the pump and observe the pellet level and refill as needed up
to the line you originally marked when you first filled the
reactor. Much like the Vodka method, dosage (amount of pellets
used) can be lowered or raised based on your nitrate/phosphate test
results. Like Vodka, overdosing pellets will cause the same
problems, low oxygen levels and cloudy water due to an increase of
bacteria. It will take at least three weeks before an effective
population of bacteria is present to begin reducing the
nitrate/phosphate level in your system. This method of carbon
dosing seems to be the most popular at the time of this
writing.
A fluidized up flow
reactor is required to use biopolymer
pellets.
There are many reputable
brands of reactors on the market.
A Two Little Fishies
Reactor is shown above. This reactor
requires a set of screens
for use with bio-polymer pellets.
A pair of Two Little
Fishies reactor screens. A template is
provided
to cut the screens to the
proper size depending on which model
TLF reactor you have
purchased.
Reef Actif (Tropic
Marin)
Tropic Marin recently
introduced a new product called Reef Actif which basically accomplishes
the same function as the above without the need of a reactor and
pump. Reef Actif is dosed by mixing the recommended amount of the
product with seawater. One half teaspoon is the dose recommended
to treat a 60 gallon tank weekly. The product is economical to
use and a 100ml container should last at least three months for the
above size tank. On larger (150+ gallons) systems it may be more
economical to use the pellets with a reactor.
Reef Actif is a fine powder
very similar to the consistency of flour. Tropic Marin states
that the polymers they use are naturally occurring marine polymers
produced by sea weeds. When mixed with sea water, the product becomes
suspended in the aquarium water where it bonds with both nutrients and
other contaminants making them available as nutrients to heterotrophic
bacteria and other animals that require dissolved organic material to
survive. These bonded nutrients are a source of beneficial
bacterial nutrition for clams and some corals such as Acroporid and
Pocilloporid corals.
100 and
500ml containers
available
A 60 gallon weekly
dose
Reef Actif is also mixed in
with Tropic Marin’s Bio Actif System Salt. Using this salt
would eliminate the use of Reef Actif or other carbon dosing products
only if weekly water changes are performed. If water changes are
conducted bi-weekly, then Reef Actif would need to be dosed on off
weeks. This salt mix is not a bargain brand at $105.00 which is
the average etailer price for a 200 gallon bucket
Users have reported excellent results with
this product.
Tropic Marin Bio Actif
System Salt
Liquid nutrient control products have hit
the market by storm recently. Although most are carbon based but
there are a few that are bacterial based which perform their job as
soon as they hit the water.
Prodibio
BioDigest
Although not exactly a carbon dosing
product, the company states that BioDigest is made up of natural
nitrifying, nitrate reducing and facultative bacterial strains selected
for their ability to convert ammonia into nitrites, nitrites into
nitrates and nitrates into nitrogen. These bacteria work together
with each strain of bacteria finishing up the work started by the
others. Some of these bacteria are capable of biosynthesizing
nitrate reducing enzymes in aerobic conditions. This in turn
enables the water to be effectively purified, nitrates and phosphates
to be reduced thereby preventing the spread of nuisance
algae.
One benefit of this product
is that it is only necessary to dose every two weeks as there are
enough bacteria present in each vial to provide effective results
during this time period.
The product is available in 6, 12, and 30
vial boxes with an average etailer price of $17.99, $26.99, and
$45.99. One vial will dose a fifty gallon tank for two
weeks.
Customer reviews of this product have been
very favorable.
Brightwell Aquatics Reef
BioFuel
Like Vodka, the main goal of using Reef
BioFuel is to provide a source of non-alcohol based organic carbon to
the heterotrophic bacteria which in turn feed on dissolved nutrients in
the form of nitrate and phosphate. In medium to high nutrient
systems, a 5ml daily dose is required. In low nutrient systems
the dose can be cut in half. Like similar products, nitrate and
phosphate tests will need to be carried out to determine a maintenance
dose. The product is available in 250ml, 500ml, 2L, and 20L
containers. A 500ml container will treat a fifty gallon tank for
approximately 100 days and has an average etailer price of
$13.49. The cost may not be very economical when compared to a
1.75 liter bottle of inexpensive Vodka for about 10
dollars which gives you 1750 milliliters of an organic carbon
source. Dosing Vodka also requires a lower daily
dose.
Advantages Of Carbon
Dosing
Lowers
dissolved nutrient levels in the form of nitrates and
phosphates.
Reduces or eliminates nuisance algae and
Cyanobacteria growth.
Improved water quality and clarity,
especially beneficial for sensitive fish such as Tangs and
Butterflyfish.
Provides a food source in the form of
bacterioplankton for filter feeders that feed on bacteria including
clams, some species of corals and filter feeders.
Eliminates the need for using carbon or
other nutrient removal media.
Disadvantages
Can
cause cloudy water if overdosed, resulting in reduced oxygen levels
which can be detrimental to the livestock in the
system.
If using polymer pellets, an initial expense
for a reactor, flow control valve, and pump will be
required.
Can initially (rare) cause an outbreak of
Cyanobacteria but this is reversed once sufficient numbers of
heterotrophic bacteria are present to outcompete the Cyanobacteria for
food in the form of dissolved nutrients.
Close
Although I have only covered
a few of the many products available, I recommend doing your homework
before purchasing, compare products and read user reviews. Carbon
dosing can be a very effective and inexpensive means to lower nitrates
and phosphates in your system as well as providing a food source for
certain invertebrates. It will also reduce, if not eliminate
nuisance algae growth and Cyanobacteria blooms in your aquarium.
I have been carbon dosing with Tropic Marin Reef Actif for the last
three months. I chose this product because I do not have room for
a reactor and associated equipment. All rock remains free
of algae other than coralline, and the water has a noticeable
improvement in clarity. Corals appear to have better color and
expansion as will be seen with all carbon based products used for this
purpose. Carbon dosing may not work in every system. It has
been noted that certain enzymes need to be present in order for the
bacteria to utilize the carbon source but this is a rare
occurrence. The alternative in this case would be to use the
Prodibio BioDigest or a similar product that provides the necessary
bacteria. Regardless of the product used, it is recommended to
perform regular nitrate and phosphate tests to determine an effective
maintenance dose.
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New Print and
eBook on Amazon
Marine Aquarium Algae Control
by Robert (Bob) Fenner
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Carbon Dosing Article
4/13/12
Hi Bob,
The carbon dosing article is also schedule to appear in the next issue
of CMA. If you wish, you can place this on WWM as well. I
believe we are weak in this subject at present.
Cheers,
James
Re: Carbon Dosing Article
Well done James. Again, I take it these are others, the
manufacturers' image work, and that we're okay to run them.
B
Re: Carbon Dosing Article
Thank you Bob. Yes, I have approval from all to use their
photos.
Would you like me to forward their emails to you?
James
Re Carbon Dosing Article 4/13/12
Thank you James... no need to, but you should hold on to for your
records. B