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What Is “Nutrient Control And
Export?”
For the purposes of this article, “nutrient control” is the
reduction of substances that can degrade water quality in captive
marine systems. “Export” is the actual
process of removal and elimination of these substances from the
system. Further, we’ll use the term “nutrient” throughout this
article to identify any substance which can lead to degradation of
water quality and the growth of undesirable nuisance algae. In
order to better understand how to control and eliminate these
substances; let us look at how they get into our systems in the first
place. Fish, invertebrates, and any other animals that we
maintain in our captive marine systems produce nutrients through their
metabolic processes, such as eating, respiration, and elimination of
waste. These metabolic substances are released into the water
column, where they can accumulate to potentially toxic levels.
Fortunately, in healthy aquariums, as in nature, countless bacteria
break these substances down into less toxic compounds. However, over
time, many of these less toxic substances remain in the water, slowly
but surely degrading the water quality, and leading to outbreaks of
undesirable “nuisance” algae, unless the aquarist takes
steps to control and eliminate them. These substances include
phosphate, nitrate, and silicate. While all of these substances
are present in healthy systems, excessive amounts of them can present
long-term problems for the aquarist. Let us look at some simple
ways to reduce and eliminate excesses of nutrients in our marine
aquaria.
Nutrient Control and Export
Mechanisms In this section, we will identify and discuss some
simple techniques that you can use to help reduce and eliminate the
accumulation of nutrients and get on the road to better water
quality. None of these techniques are revolutionary; most have
been around as long as the aquarium hobby. However, in our quest
to achieve optimum water quality and control nuisance algae, we often
overlook some of these basic techniques in our quest for “The Big
Solution” to our problems. Source
Water Water contains numerous substances which can
affect the plants and animals that live within it in both positive and
negative ways. Of particular concern to us as hobbyists are
substances such as nitrate, phosphate, and silicate, which, both
individually and collectively contribute to lower water quality and
outbreaks of nuisance algae. When using source water, such as tap
water, for “topping off” or mixing new water for our
aquariums, we are often inadvertently fueling the growth of nuisance
algae by providing them with a continuous source of basic
nutrients. One of the best ways to eliminate nutrients from
source water is to employ some form of pre-treatment, such as reverse
osmosis and/or deionization. RO/DI units are now available to the
hobbyist in a wide variety of configurations and prices, and allow the
hobbyist to produce virtually pure water at a very low cost. Do
keep in mind, however, that the membranes on these units do need to be
maintained and/or replaced periodically if they are to continue to
perform their function as a means of water purification. The frequency
of RO/DI unit maintenance is largely dependent upon how much use the
unit gets, and the amount of undesirable substances which these units
are expected to remove from the water. Many hobbyists who use
RO/DI units seem to forget that they do need this maintenance, and it
is often overlooked until water quality begins to decline and nuisance
algae start to manifest themselves in the aquarium! Do not
neglect the maintenance of your water purification system- it is on the
“front-line” of your battle against excessive
nutrients! Mechanical
Filtration Media A vast array of mechanical filtration media is
available to the hobbyist, offering a wonderful means of removing
particulate matter and detritus from the aquarium on a continuous
basis. These media range from the ubiquitous filter cartridges
and ceramic “noodles” found in power filters and canister
filters, to the “micron” filter bags, sponges, and
polyester “prefilters” utilized in sumps and
overflows. These media are intended to remove gross
particulate before it can accumulate elsewhere in the system.
However, many of these mechanical media are “victims of their own
success,” if you will, and begin to accumulate large quantities
of gross particulate and detritus, which slowly breaks down, and leads
to the formation and accumulation of nitrate and phosphate.
By regularly cleaning and replacing these
mechanical media, it is possible for the hobbyist to remove large
quantities of undesirable matter from the system before it begins to
break down and degrade the aquarium’s water quality. Many
of these filter media need to be cleaned and/or replaced several times
a week, or they can easily become a major contributor to nutrient
accumulation in the system. Some hobbyists have accumulated
enough prefilters and filter bags to “rotate in” a new one
several times a week, or even daily. Trust me on this-if you
replace your mechanical media on a frequent basis, you will see a very
noticeable improvement in water quality and a measurable reduction in
nitrate and phosphate accumulation within your system!
Protein
Skimming One of the very best means of nutrient control and
export for captive marine systems is the continuous use of a protein
skimmer. It is arguably the best means of removing organic
substances from the aquarium water. An efficient, well-maintained
skimmer can reduce the amount of organics present in the water before
they break down and begin to accumulate. There is little argument
among aquarists as to the effectiveness of protein skimming for
removing these compounds. However, there are many different
opinions as to which type of skimmer, and which model, is the
“best.” The review and comparison of the
relative merits of different skimmer designs is beyond the scope of
this brief article; suffice to say that the inclusion of a protein
skimmer in the marine system is, for most of us, and absolute
necessity, and a key contributor to the maintenance of a successful
aquarium! Of critical importance when using a skimmer is its
placement within the system. A skimmer should be placed at a
location within the system where it will receive “raw,”
unfiltered water, ideally from the surface of the aquarium. This
water has the highest concentration of organic materials and other
substances that should be removed from the system. The skimming
should ideally take place before any other filtration occurs, with the
possible exception of gross particulate removal. This will ensure
that the skimmer is receiving the largest amount of organics to work
with. A skimmer should be adjusted so that it produces
at least one to two cups of dark, yucky smelling stuff per
week. Stable, “dry” foam within the neck and
collection cup of the skimmer is a sure sign that you’ve found
the “sweet spot” within your skimmer’s operating
parameters. One thing that is a “constant” with
protein skimmer use is the necessity for frequent maintenance of the
skimmer itself. The sludge that accumulates within the neck and
collection cup of your skimmer actually inhibits the production of
desired foam after several days, so for optimum performance, a skimmer
should be cleaned at least once, possibly even twice, per week.
At the same time, inspect and/or clean venturis, injectors, and
airstones which may be present in your skimmer. You’ll be
surprised at the increased efficiency that will result from regular
skimmer maintenance! A well-maintained, properly set-up protein skimmer
may be the best single contributor towards optimal water quality and
nutrient control in a closed marine system. Water
Changes Another one of the most basic aspects of aquarium
husbandry (and one of the best means of achieving nutrient control and
export!) is the performance of regular, modest water changes in your
system. In my opinion, smaller, more frequent water changes
are preferred over larger, less frequent ones, and are much less
labor-intensive. Try changing as little as 5% of tank volume on a
twice-weekly basis, and you’ll be astounded at the difference
this will make in your system! Fish will be livelier and more
colorful, corals will open up like you’ve never seen them do
before, and levels of dissolved organic substances, such as nitrate and
phosphate, will decrease significantly. Frequent water changes
allow the aquarist to help dilute and reduce the concentration of waste
products from the system before they begin to accumulate as
nutrients. This, in turn, will result in less potential for
nuisance algae growth, and a more stable system. Remember to use high-quality source water when
mixing up your saltwater for water changes. Be consistent,
methodical, and siphon out as much detritus as you can from the
rockwork and other areas from the aquarium. Frequent water
changes also give the hobbyist the added advantage of being “in
touch” with the system on a very regular basis, resulting in a
better understanding of just what’s going on within his or her
aquarium. As the old hobby saying goes, “nothing good
happens quickly in a marine system,” so the benefits of frequent
water changes will begin to manifest themselves gradually-but they will
become obvious after a brief period of time. Give more frequent
water changes a try! Bioload The best (and worst!) part of the marine aquarium
hobby is choosing among the hundreds of available creatures in order to
stock our aquariums. With new corals, fishes, and other
invertebrates hitting the market on a regular basis, we are constantly
tempted to add new animals to our systems. High tech protein
skimmers, filters, and various “additives” often provide
the hobbyist with a false sense of security, lulling us into believing
that our system can “handle” an absurdly high biological
load. Despite our best intentions, the temptation to add
“one more” fish, coral, or invertebrate can risk upsetting
he delicate balance that occurs within our systems, and creates the
potential for an over-crowded, unsanitary, and unsustainable
aquarium. It is important to “under crowd” our
systems with animals, so that we may create a better life for our
captive specimens. Over-crowded aquariums result in excess amounts of
metabolic wastes, which will create seriously degraded water quality in
little time. An aquarium with a very high bioload
will offer little “margin for error” on the part of the
aquarist. The very real potential exists for the dreaded
“crash” of the system, a horrible situation
where the toxic metabolites accumulate to rapidly for the biological
filtration mechanisms to process and reduce them into relatively
harmless substances. Utilize common sense when stocking your
aquarium, both in terms of the number and types of animals that you are
attempting to keep. The bottom line here, dear reader, is to
resist that temptation to add more specimens to your system than it can
handle! Foods and
Feeding One of the easiest to control sources of excess
nutrients in captive systems is food. Frozen and other prepared foods
contain large quantities of phosphate and other organics that can
seriously degrade the water quality in even the largest
aquariums. When feeding frozen foods, it is of utmost importance
that you do not simply dump the food, frozen juice and all, directly
into your aquarium. The processing juices contain huge amounts of
nutrients that may not be utilized by the life forms in your aquarium,
and thus accumulate, creating optimal conditions for nuisance
algae. Always thaw out frozen foods slowly in a container
of water, then dump out the water, and feed the food with a toothpick
or other small implement. Yes, this technique is a bit more tedious,
but it will significantly reduce the amount of excess organics that
enter the aquarium. It is a basic tenant of aquarium keeping that
you should only feed as much food as your fishes will consume in a
reasonable length of time, and that uneaten food should be removed
before it has a chance to decompose and affect water quality.
When utilizing liquid foods, such as those
developed for invertebrates, be sure to use a syringe or
baster to “target feed” the animals. Some
hobbyists actually remove animals such as Tubastrea, and even small
clams, to a separate container to allow them to feed without fear of
polluting the display tank. The extra time it takes to do this
can reward the diligent aquarist with much higher water quality, and
less possibility of nuisance algae appearing in the display tank.
Additives Fortunately or unfortunately, we live in an era
where technology makes it possible to produce all sorts of additives,
“water conditioners”, trace elements, and other
“extracts” which are supposed to somehow make keeping
marine aquariums easier. Manufacturers tout the effectiveness of
their products in enhancing invertebrate growth, supplementing
fishes’ diets, and helping to create “natural”
conditions in our captive aquaria. Some of these products are
excellent, some not so good, and still others are outright junk.
When utilizing any additive, you need to ask yourself why you are using
it! If you are trying to “push” corals to grow
faster, or make invertebrates grow larger, or even attempting to
cultivate macroalgae, some thought must be put in as to what these
products are doing to the overall water quality. Some
“additives” contain high quantities of sugars and other
micronutrients which, if added without a lot of diligence, can turn an
otherwise healthy, attractive aquarium into a virtual cesspool!
There are many elements that can be replaced in captive systems by simply conducting regular water changes with quality source water and a good salt mix. If you are adamant about using some additives (such as iodine, which is a commonly used additive), be sure to conduct water tests for that element, to make sure that you are not “overdosing” your system. In fact, it is a good general rule of thumb to not add anything to your aquarium unless you understand exactly what it will do to the water quality, what benefit you expect from the product, and what the long-term implications are for its use. Use of
Chemical Filtration Media An excellent means of nutrient control and export
is to utilize some form of chemical filtration in your system.
There are many different products on the market that are formulated to
remove everything from ammonia to phosphate, and many substances in
between. Use of commonly available, high quality activated carbon
on a regular basis in your aquarium will help to reduce excess
nutrients continuously. Other fine products include specialized
media, such as PolyFilter, which has an affinity for a wide variety of
organics. Of particular importance when utilizing chemical
filtration media for nutrient control is the regular replacement of
these media. In order to do the job expected of them, these
products must be inspected and replaced as needed. If used in
accordance with the manufacturer’s instructions,
chemical filtration media can provide the aquarist with a safe,
effective means of nutrient control and export. It is my opinion
that every aquarium should utilize some form of chemical filtration
media on a regular basis. These media provide a convenient and
cost-effective supplemental means of removing undesirable substances
from the water with minimal effort on the part of the
aquarist.
Macroalgae Macroalgae play an important role in closed marine
systems. They utilize nutrients, such as nitrate and phosphate,
which are found in abundance in most aquariums. As they grow,
they take up required nutrients from the water column.
The use of macroalgae in marine aquariums is a
matter of personal preference, but can provide the hobbyist with an
affordable, natural means of exporting excess nutrients from the
aquarium. Many hobbyists grow and harvest
“purposeful” macroalgae, such as Chaetomorpha, Gracilaria,
Halimeda, and Caulerpa somewhere in their systems in order to assist in
the control and export of excess nutrients. By carefully
cultivating and harvesting the macroalgae on a regular basis, you are
literally removing excess nutrients from the aquarium. The
macroalgae may be grown either in a separate section of a sump, algal
turf scrubber, or even a refugium, depending upon the hobbyist’s
preferences. The degree of nutrient export provided by
macroalgae is largely dependent upon the growth rate, density, and
quantity of the macroalgae harvested. Under optimal conditions,
some species of macroalgae can achieve tremendous growth rates,
providing the hobbyist with a wonderful means to export nutrients from
his or her system.
Deep Sand
Beds Recent research by scientist and hobbyists alike
has identified a superior means of nitrate reduction and nutrient
export by utilizing a deep bed of fine aragonite sand in the aquarium
proper, or in a specialized remote sump. Deep sand beds (3
to 8 inches or more) have been proven to foster natural biological
processes that serve to reduce nitrate and efficiently process organics
in captive systems. Some advocates of deep sand beds, such as Bob
Goemans and Sam Gamble, suggest the construction and use of a plenum in
conjunction with a sand bed, which provides significant nitrate
reduction capabilities. Other authors and hobbyists advocate simply
placing the suggested layer of sand directly on the aquarium bottom to
construct their sand beds. Regardless of which approach to a deep sand bed
the hobbyist utilizes, the benefits of a properly constructed,
well-maintained deep sand bed are dramatic and impressive. Deep
sand beds are a valuable tool for the hobbyist to help maintain a more
natural, biologically stable system, and provide a simple, efficient
means of controlling and exporting nutrients from captive
systems. Refugia One of the relatively new concepts in marine
aquarium and reef keeping, but one that has caught on dramatically, is
the use of a refugium attached to the main system. As their name
implies, refugia provide a protected place where delicate organisms can
grow and reproduce, free from predation and harassment from other
animals. Many of the organisms which grow in refugia efficiently
utilize and process nutrients found in the water column as
part of their natural growth processes. Organisms such as feather
duster worms, amphipods, copepods, small anemones, and even sponges,
provide an amazing natural “filtration” service for the
aquarist, and offer the added benefit of providing the system with a
supplemental food source through production of plankton and other
animals that find their way into the display aquarium. The
implementation of refugia into captive displays is almost a
“sub-hobby” of its own, and should definitely be explored
by hobbyists for its rich potential benefits. Other
Natural Methods Some aquarists, such as Steve Tyree, have
suggested the potential of sponges and sea squirts as part of
multi-level “zonated” filtration for reef aquariums.
This concept is wide open for exploration by adventurous aquarists, and
may offer an incredible means of nutrient control and export which has
yet to be fully utilized within the hobby at this time. Other
authors, such as Anthony Calfo, point out that even so-called
“pest” animals, such as the dreaded Aiptasia anemone, can be utilized in a
sort of “scrubber” as another natural means of nutrient
export. Still other hobbyists are experimenting with autotrophic
animals, such as the soft coral Xenia, to perform the same
function. With a bit of experimentation, and a lot of
persistence, the intrepid aquarist may discover entirely new means of
nutrient control and export for captive systems. There simply is
no telling what types of creatures and methods may work in this
capacity! Conclusion I hope that this brief review of nutrient control and export methods has encouraged those of you who are struggling with high nitrate or phosphate levels, unstable water chemistry parameters, and nuisance algae growth to explore some of the methods that we touched on here. None of them alone is the “one” answer to all of our problems. However, by understanding what means of nutrient control and export are available, and how they can be implemented, you may just find the key to solving a problem that has caused you considerable grief! One of the great things about our hobby is the ability of hobbyists at all levels to contribute to the general knowledge of marine aquarium keeping. Perhaps you have found a better way to approach the problem of nutrient control and export, or simply have modified an existing approach to better suit your needs. Either way, be sure to share your findings with others, so that the hobby, and most importantly, the animals which we keep, can benefit from your labor and research! Bibliography:
Calfo, Anthony. “Book of Coral
Propagation,” Reading Trees Publications, Monroeville, PA,
? 2001. Fenner, Robert. “The Conscientious
Marine Aquarist,” Microcosm Ltd, Shelburne, Vermont, ?
1998. Tyree, Steve. “The Porifera (Living
Sponges), D.E. Publishing, Rancho Cucamonga, CA, ?1998.
Goemans, Bob, Ph.D. “Live Sand Secrets,” Marc Weiss Companies, Inc., Fort Lauderdale, FL, ?1999. |
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