On this page, we would like to continue our
discussion on different types of chemicals
encountered in maintaining saltwater aquarium.
The two major topics that we want to discuss
are Reverse Osmosis and Ozonization. To begin
with our discussion, let us look at the source
for all of our saltwater aquarium water -
tap water.
Table of Content
Regardless of the size of your tank, all
of us use the tap water to mix with the salt
to produce the saltwater for our tanks. Unfortunately,
the tap water that comes straight from our
pipe does not necessary be perfect for our
saltwater aqaurium to use. The natural sea
water does not contain as much minerals as
the tap water connected to our house. The
natural sea water is oligotrophic, which means that the natural sea water
is not rich in nutrients.
Reverse Osmosis is meant to remove the harmful
chemicals that are present in the saltwater
aquariums. These harmful chemicals are phosphate,
silicate, and nitrate. The first two chemicals, phosphate and silicate,
are usually present in tap water. The nitrate,
however, is produced in the biogogical decomposition
of the nitrogeneous cycle. It is the end
product of the nitrification, the second
stage of the denitrification process. Remember
that the nitrification process is to turn
ammonia and ammonium to nitrite and nitrate,
so that the nitrogeneous compounds can be
further dissimilated.
In the extensive discussion of protein skimmers,
we have learnt that the break-down of the
nitrogeneous organics are partly taken care
of by the living organisms inside the tank.
However, since the rate of producing the
organics is usually much faster than the
rate of breaking down the organics, it is
necessary to have a protein skimmer installed
in all saltwater aquariums. The job of a
protein skimmer is to remove the organics
before they have been properly broken down.
This, in essence, the amount of organics
for the biological load in your tank to handle.
The purpose of using a Reverse Osmosis device
is similar in that it is to remove the phosphate,
silicate, and nitrate before an excessive
level is reached inside the tank.
In fact, a Reverse Osmosis device is a lot
more powerful than we just described. It
should be considered as the first safety guard against problems that may occur in your
tank. This is very true if you are living
in area where drinking from tap water is
problematic, like Europe and U.S. The Reverse
Osmosis device is usually connected directly
to the water mains, and hence, you should
consult with a plumbing consultant before
it is installed. The water will first be
passed through a pre-filter filled with activated carbon to remove chlorine - commonly added to our
tap water in the water treatment plants.
The water is then forced through a mechnical filter to remove the large particles from the stream.
The key of a Reverse Osmosis device is the
membrane that the water is then forced through. The
membrane is an unltra-fine grid. The water
is passed through the membrane at a pressure
that is higher than the osmotic pressure.
As a result, the membrane keeps most of the
organics and inorganics dissolved in the
water before the water enters the sump.
So what does it mean when the water is passed
through the membrane at a pressure higher
than the osmotic pressure? Let us review
the Osmoregulation that we have discussed
in previous pages. Since the saltwater aquarium,
where you have just bought your fishes from,
is very likely to have a different chemical
condition than that of your own tank, the
fishes may have to adjust their own bodies
to the new condition in your tank. The adjustment
is the active transport of the high concentration
of chemicals inside the bodies out to the
ambient water, or vice versa. The result
of the adjustment is to distribute the chemicals
evenly among the regions having a different
concentration levels of the chemical previously.
The chemicals flow from high to low concentration.
This is Osmosis, or diffusion.
However, immediately you see that this does
not fulfill what we want to achieve. We do
not want more phosphate, silicate, nor nitrate
inside our tanks. We want to keep them away
from our tanks. That is, we must reverse
the process of Osmosis. We want to force
these chemicals to go from low concentration
regions to high concentration regions. Hence,
the name of Reverse Osmosis. There is a very helpful analogy to enhance
the understanding of the Reverse Osmosis.
If you imagine an electric circuit as a waterfall,
the stream of electrons (because of gravity)
is only going to flow from the a high pressure
point (or high voltage) to a low pressure
point (or low voltage). To keep a circuit
running, there must be a battery to pump
the water from the low point to the high
point. The Reverse Osmosis device is like a battery
in a circuit in that it raises the voltage
from a low to a high point.
When do you need a Reverse Osmosis device?
The device is required in regions when the
tap water is highly mineralized. Chemicals
such as nitrate, phosphate, silicate, alumium,
copper, zinc are to be removed by the device.
Where do the alumium, copper, and zinc come
from? They can come from the degrading of
your old pipes connecting to your water system.
Copper and zinc, and os
in the tank. The mineralization, however,
produces color substances that give your
water a yellow hue. Activated carbon can
be used to remove the tinge. However, the
problem of using activated carbon is the
potential bleaching of corals. Hence, most
people prefer the use of an ozonizer instead.
Ozonizer had been mentioned a couple of times
before when we were discussing the use of
Redox devices. Ozone (O3) is a very powerful oxidant. That is, it can be used to break down the
nitrogeneous organics into inorganics, or
to finish the decomposition process, without
releasing any harmful immediate products,
like nitrite. Since ozone is toxic, care must be taken
when you choose to use the ozonizer. First,
you should never connect the ozonizer to
the tank directly. (Same as denitrification
filter because its effluent is extremely
low in oxygen.) Second, you must have a Redox
device to monitor and control the ozonizer.
The usual set up is to connect the ozonizer
to the air in-take of the protein skimmer,
so that the ozone gas can be used up as soon
as possible.
Reverse Osmosis Devices are very popular
in United States, however, not so popular
in Canada. But, the use of such a device
is still recommended since the quality of
your tap water is a dominating factor in
determining how the quality of your tank
is going to be. The simple reverse osmosis
device is a CORALIFE product, the PURE-FLO
device with a celluose triaceate (CTA) membrane.
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Here is the CORALIFE PURE-FLO reverse osmosis
device. You can think of the entire device
as one big filter which takes water from
your house's plumbing system (the yellow tube), filters it, and passes through the
other two tubes. The blue tube is the purified water and the red tube is the waste water, or highly mineralized
water. But remember that the device should
not be connected to the sump directly. The
red tube should be fed to a drain. The purified
water coming out of the blue tube should
be collected in a plastic container. Since
the purified water does not have much minerals,
you can then mix the water with salt and
add the amount of electrolytes to fit your
own need.
It is recommended in the manual that a clean
plastic container should be used instead
of a metal container. Inappropriate storage
containers can introduce salts and other
ions (so make sure that the container is
free of any detergent residues) to the purified
water.
Before you actually use the solution, do
not forget to check the pH and hardness levels.
If your tank is having any problem, you can
add the medication to the solution as well.
You can also check for other chemical levels
before you put the water into your sump.
Now let us look at the two components of
this device, the sediment pre-filter and the membrane housing. The sediment pre-filter is the top cyliner
and the membrane housing is the bottom (and
bigger) cylinder. The membrane that comes
with this device is a celluose triaceate
(CTA) membrane. (There is another type of
membrane, which we will mention shortly.)
The installation and assembly process are
very simple and only component that you need
to assemble for a new unit is the membrane.
The pre-filter shoould be replaced every
6 months, whereas the membrane should be
replaced annually. The replacement, of course,
also depends on the water quality of your
source water as well. You may need to replace
the parts more frequently than recommended.
Note that the sediment pre-filter included
in this device is only the mechnical filter,
but not the carbon filter mentioned in the
general principle of a Reverse Osmosis device.
.jpg)
Here is another Reverse Osmosis device from
CORALIFE. The principle of this device is
almost identical to that with the CTA membrane
product. The difference, however, is also
quite obvious. It handles a larger volume and it has a second filter besides the sediment
pre-filter, the right (vertical) cylinder.
The carbon filter is the left (vertical) cylinder. The white
cylinder is the membrane housing. The other
feature that makes this Reverse Osmosis device
better than the one shown above is that this
device comes with a thin - film composite (TFC) membrane. The TFC membrane is an inheritally
better membrane than the CTA membrane.
The general installation, assembly procedure,
and the maintainance details are identical
to the CTA membrane. However, there are a
few points that you want to keep in mind:
Source water, the water to the yellow tube
must be chlorinated and cold at all time. The devices requires that the source water
has to be chlorinated so that micro-biological
activity in the water that can cause bacterial
degradation of the membrane can be eliminated.
This is not a problem for people living in
Calgary and usually not a problem in North
America.
If you are using a new membrane, or a membrane
that you have not been using for a while,
it is necessary for you to flush the membrane
before it can be used. The flushing is to ensure the anaerobic
condition that may have developed in the
membrane.
The last point is about storing the membrane.
The membrane should never be stored dry. Please consult with the manual that comes
with the device for the details.
To complete our discussion, we feel that
it is better to cover the basic knowledge
of a few other chemicals that we did not
cover on the More Cheimcals page and to help
you appreciate the importance of a Reverse
Osmosis device, rather than simply saying
"they are harmful and must be removed."
Silicate
Silicate (SiO2) are most commonly encountered in setting
up a new marine tank. Silicate is the nutrient
of a type of algae called diatoms. Diatoms
make use of silicate molecules to construct
their cell walls. As a result, excess silicate
leads to a bloom of diatoms in the tank.
The diatoms are usually not a problem once
the biological cycle is established and the
other types of algaes dominate the tank.
Thus, we see that the diatoms, in fact, are
constantly competing with the other algaes,
such as the red and brown algaes for the
dominant position. Excess silicate that leads
to the diatoms dominating in the tank discourages
the normal growth of the other good algaes.
Remember algaes are good for photosynthesis
and partly responsible for the chemical decomposition
in the tank.
Phosophate
Phosophate are set free in the decomposition of plants,
and other dead micro-organisms. (Remember
the nutrient bombs issues.) What may not be commonly known
is that there is a pool of phosphate present
in the tank at all time. The phosphate molecules
are commonly found in water in the form bound
to the other chemicals. The interesting point
is that the pool of phosphate is inversely
related to the pH level in the tank. That
is, more phosphate molecules are released if
the pH level is low than if the pH level
is high. Since phosphate is an essential nutrient
to algaes, the release of the phosphate molecules
will result in an uncontrolled growth of
algaes. This gives another reason for you
to monitor your pH level closely. (Fortunately,
phosphate molecules can be removed effectively
by protein skimming.)
Nitrite and Nitrate
Nitrite (NO2-) and Nitrate (NO3-) are correspondingly the immediate and the
end products of the Nitrification process.
Nitrification process, if you remember, is
the process of turning ammonia and ammonium
into nitrite and nitrate and they are also
nutrients to algaes. However, nitrite does
impose a more serious threat than nitrate
in that a high concentration of nitrite inhibits
the nitrification process and nitrite poisoning
can generate respiratory difficulty for your
fishes. This can easily kill your fishes.
As you can see that most of the test kits
available are quite complicated and tedious
to use. The test kits that you see so far
on this page usually has 3 to 5 different
chemicals that you must mix with during the
test. In fact, you can do better than this!
Below is a picture of such a product:
The first four on the left are different
test strips for pH, Alkalinity, Nitrate,
and Nitrite. The other two are eliminators.
The eliminators are to be used when the result
of your tests showing that one, or more,
of the chemical levels have been exceeding
what it should be. To preform the test, all you need to do
is to dip the end with chemical on it into
the water and hold it for a few seconds and
wait for the chemical to turn its color once
you have taken it out of the tank. The results
are quite accurate and the colors are quite
easy to distinguish. If you have used any test kits before, you
know that it is sometimes quite difficult
to match the color of the test result with
the color chart included in the test kit.
These test strips have also solved the problem
for you. Because of these two advantages,
they have become the most popular test kits
in our shop!
Here, we can summarize the basic problem
of having excessive silicate, phosphate,
and Nitrate in our tanks. The three chemicals
are problematic because they are nutrients
to different types of algaes. The excess
levels of these chemicals are going to induce
a bloom of algaes that are not supposed to
dominate the tank. This then screws up the
normal cycle in your tank. While phosphate
molecules can be removed effectively by protein
skimming, the silicate and nitrate can only
be removed by Reverse Osmosis.
Calcium
Calcium is definitely needed for reef tanks.
Same as our own bodies, corals need Calcium
to build their skeletons for growth. There
are many different ways to add calcium to
your tank, however. Do you remmeber the Calcium
Reactor and Carbon Dioxide Reactor (together
with a pH controller) set up discussed on
the More Chemical page? That is an advance
system that you can install to your tank.
While the system offers different advantages
to us, it can also be quite expensive! The
most common way to add calcium to your tank
is to use the chemicals that have been prepared
for your own tank. (The CORALIFE product
is only shown here as a sample; we do carry
other products as well.) The Calcium test
kit is similar to those shown below. It comes
with a few chemicals that you can mix with
the water sample.
Strontium
It has been widely accepted that Strontium
is highly essential in the formation of the
coral skeletons. The coral skeletons are
built of calcium carbonate and also strontium
carbonate. There have been questions concerning
the real significance of adding Strontium
to the tank. You may be able to give away
without adding much Strontium to your tank.
However, we do use Strontium in our own tanks
and test the Strontium levels constantly.
So we do advice the use of Strontium in saltwater
aquariums.
Vitamin
These three products contain vitamin that
you can safely add to the tank. You may consider
adding this and the trace elements solution
to the plastic container and wait for the
solution to be settled.
Iodine (I) is necessary for the red and brown algaes
to grow. Iodine is also desired because when
combined with the other trace elements, a
UV protective pigments can be formed. The
protective pigments can then provide a guard
against bleaching. Here, we can see a potential drawback of
using a Reverse Osmosis device: If the pre-filter
of the Reverse Osmosis device uses too much
of activated carbon, the trace elements can
also be greatly reduced by the active carbon.
Hence, bleaching of corals results.
There is indeed another reason for the use
of activated carbon. The by-products arise
in the decomposition process are essentially
nutrients to the algaes or other micro-organisms
in the tank. The mineralization, however,
produces color substances that give your
water a yellow hue. Activated carbon can
be used to remove the tinge. However, the
problem of using activated carbon is the
potential bleaching of corals. Hence, most
people prefer the use of an ozonizer instead.
Ozonizer had been mentioned a couple of times
before when we were discussing the use of
Redox devices. Ozone (O3) is a very powerful oxidant. That is, it can be used to break down the
nitrogeneous organics into inorganics, or
to finish the decomposition process, without
releasing any harmful immediate products,
like nitrite. Since ozone is toxic, care must be taken
when you choose to use the ozonizer. First,
you should never connect the ozonizer to
the tank directly. (Same as denitrification
filter because its effluent is extremely
low in oxygen.) Second, you must have a Redox
device to monitor and control the ozonizer.
The usual set up is to connect the ozonizer
to the air in-take of the protein skimmer,
so that the ozone gas can be used up as soon
as possible.
If you are interested in purchasing the Reverse
Osmosis device with CTA membrane, we have a good news for you. The
device shown above is the last one in our
stock. Hence, we are willing to sell it at a special price
$ 100 CAN. (Regular price $160 CAN). If you are interested,
please contact us. The special offer is available
on a first-come-fist-serve basis. Don't miss
it!
© Wai's Aquarium Ltd, 2000, 2001. All rights
reserved.