Protein skimmers are so critical that every saltwater aquarium must have one. The protein molecules that concern us here are the same proteins generated from dead algaes and corals, and regular metabolic behavior. The whole point of bio-filteration is to remove these protein molecules in the water. The proteins can be removed by algaes through their photosynthesis and bacteria through the denitrification process. However, nitrification (the second stage of the denitrification process) usually happens in a much faster rate then the denitrification process. That is, the tank produces more than it can clean up. So, there are generally more proteins in the water than these micro-organisms can handle. This introduces the need of the protein skimmer.
What a protein skimmer does in your tank is that it removes the protein molecules directly from your tank before they are taken care of by the bacteria. In other words, your protein skimmer can significantly reduce the amount of nitrogeneous molecules that bacteria in your tank must clean up. For this reason, we always recommend to our customers to get the best protein skimmer that you can afford because an efficient protein skimmer makes a very big difference in your tank.
The operating principle of all protein skimmers involves three stages: generate fine air bubbles, allow the negatively charged protein molecules attached to the fine air bubbles in the reaction chamber, and collect the dry foam (the nitrogenous waste) in the collection cup. Based on this simple understanding, we can list 6 main criteria that you may consider when you are getting a new skimmer or when you are determining how efficient your skimmer is.
Amount of Air Bubbles Produced - The functionality of your protein skimmer primarily depends on the effectiveness of the adsorption of protein molecules to the air water layers. The amount of air bubbles produced by your skimmer is one of the major parameters in protein skimming.
Quality of Air Bubbles Produced - The quality of air bubbles produced means how fine the air bubbles are. When the protein molecules are attached to the air bubbles, a mono-molecular layer is formed. So the finer the air bubbles are, the more surface area for the protein molecules to be attached to in a given volume. Together the amount and the quality of the air bubbles produced represent only one thing - surface area for the protein molecules to be attached to. What we are saying here is that the more and the finer the air bubbles are, the better the skimmer is.
Air - Water Contact Time - The second stage of protein skimming is to let the air bubbles to come into contact with the protein molecules. So the longer the time for the bubbles to come into contact with the protein molecules, the higher the probability for the protein molecules to be carried away. For this reason, we always want to have the maximal contact time. In fact, to ensure the skimmers to have their maximal air-water contact time, most of the skimmers manufactured use the same technique which is simply to have the water source (of the skimmer) near the bottom of the skimmer and so the air bubbles have the maximum amount of time to rise to the top of the reaction chamber.
Efficiency of Dry Foam Collecting - Collecting dry foam is the last step in protein skimming. However, it is not as easy as it sounds. When the air bubbles have the protein molecules attached on them, the air bubbles will still be rising up to the top of the reaction chamber. However, only some of the air bubbles will be collected in the collection cup since the other air bubbles will be too heavy to be raised to the top. These bubbles are too heavy because they have water molecules also attached on them. As a result, the air bubbles that have the protein molecules attached and are finally collected are called the dry foam. Whereas the air bubbles that cannot reach to the top are called the wet foam. So collecting the dry foam affects the efficiency of the skimmer in that if the wet foam is also collected, the waste that you have collected in the collection cup is diluted. Therefore, for the same volume of waste that your skimmer has collected, you have less waste than it is supposed to be.
Regular Maintenance of the Skimmer - The basic principle behind the protein skimmer is that the water surface must be electrically charged. However, if the food that you feed to your corals and fishes contains fat, the left-over food in the contact chamber is going to form a layer that can break the foam easily. This lowers the probability for the protein foam to be collected. For this reason, the contact chamber should be cleaned regularly.
Gallon Handling Capacity - The number of gallons the protein skimmer can handle is always the first number that you look for when consider of getting a new skimmer. However, for North America products, their rated values are usually higher than what they are really capable of than the similar products manufactured in Europe. So if you are going to get a North American product, it is a wise decision to get one that has a capacity slightly bigger than the one you need. The gallon handling capacity also depends on how efficient your overall biological filteration system is. When in doubt, please check with your local dealer for a suitable capacity.
Noise Level - All venturi protein skimmers make noise when they are operating. But some are particularly noisy. If you decide to have your tank in your office, you may not want to have a really noisy skimmer. This is particularly important when you are using a big skimmer for the obvious reason that the bigger the motor is, the larger the noise it produces.
Now let us look at the simplest protein skimmer. In our discussion, you will see that the simplest protein skimmer is not a very good skimmer in that it fails to give good ratings in the major criteria listed. In our discussion, we will look at 5 different skimmers and compare their performance according to the 6 criteria.
Lee's Protein Skimmer
Here we have shown an inexpensive protein
skimmer from Lee's Aquarium & Pet Products
just to illustrate the basic principle described
in the following discussion. Please click on the left picture to see the
full size of it. The terms used in the following discussion
correspond to the ones shown on the full
size picture. The right picture is taken
in our store. It shows the simple protein
skimmer at work. The bubbles is formed in
the contact chamber and the waste material
is in the collection cup. The waste should
be cleaned regularly.
A protein skimmer is basically a tube, called
contact chamber, with a cup on the top to
collect the waste which you must remove regularly.
The contact chamber has an air stone sunk
at the bottom and is a place where you normally
see a lot of bubbles rising from the bottom
of the chamber to the collection cup (see
the right picture above.) The electrically
charged amino- acids molecules adhere to
the air bubbles, by which these charged molecules
can be brought to the collection cup at the
top. When the air bubbles reach the top of
the foam riser tube, they come into contact
with the air inside the collection cup, and
hence, these bubbles form the foam that you
see in the collection cup.
You may notice that not all the foam formed
have the protein molecules adhered. You are
right. There are two types of foam here:
normal and protein foam. We only want the protein foam to be collected
in the collection cup and the normal foam
to be returned to the aquarium. The normal foam can be quickly broken up
and to be returned through the return tube.
They are easily recognized as the steam of
bubbles of identical size going back to the
aquarium. To see the bubble stream clearly. The waste that we want to remove is a brownish
protein liquid (after settled) is called
adsorbate.
If you want your skimmer to work at its peak
efficiency, use air stones that can generate fine air
bubbles. The finer the air bubbles are, the larger
the probability for the protein molecules
to be stuck on the bubbles. The air stone
should also be kept at the bottom because
this ensures that the air bubbles have the
maximum amount of time to come into contact
with the protein molecules. This again increases
the probability for the protein molecules
to be collected.
Now let us look at why this simple protein skimmer is not the optimal choice for a reasonably big, such as 90 Gallon, tank. The source of the air bubbles for this Lee's product is an air stone. Due to its very limited size, the amount of air bubbles produced is very limited also. Moreover, as the air stone has been used for a while, the air stone degrades. That is, algaes are formed on the surface of the air stone which reduces the surface area for the air stone and so the amount of air bubbles produced is going to decrease also. As the air stone degrades, we may also wonder if the quality of the air bubbles can maintain for its regular operation. The other drawback of this little skimmer is that there is a very small current flow into the chamber so that greasy material can easily build up on the inner surface of the contact chamber and these greasy material simply reduces the amount of air bubbles that can reach to the top of the chamber. (The greasy material refers to those left-over food discussed in the Regular Maintenance of the Skimmer criterion.) There is another obvious problem with this skimmer which relates to its efficiency of collecting the dry foam in the collection cup. However, for these 3 major reasons, we see that this skimmer is only good for small tanks or can only be used as supplement to a main system.
On the left is another portein skimmer, Big
Monbasa. The big Monbasa has a much higher
gallon handling capacity than the simple
Lee's product. Unlike the Lee's protein skimmer,
the Big Monbasa skimmer is actually one of
the venturi skimmers. That is, it does not use an air-stone to
generate its air bubbles. It uses an external motor to mix and pump the air and water into the
contact chamber.
When fully assembled, the Big Monbasa skimmer
has a basket attached to the back of the
skimmer. Inside the basket, there are 2 sections.
One of the sections is where you put the
venturi pump (for the incoming water) and
the other section is where you put a soft
rubber sponge (included) (for the out going
water). The venturi pump included in the
box is actually nothing more than a simple
power head which allows you to pump water
into the contact chamber. However, the pump
also has an inlet for sucking air into the
pump. When the pump is operating, the mixing
of the air and the water, which occurs inside
the pump, generates the air bubbles for the
skimmer. For this reason, it generates a much higher volume of air
bubbles than the simple Lee's skimmer.
The contact chamber has as inlet directed
in such a way that when the water (together
with the air bubbles) enters the contact
chamber, the incoming water must be shooting
downwards to the bottom of the chamber. This
meets the requirement of allowing the maximal air-water contact time
for the protein molecules to be attached
on the air bubbles.
After the generation of the air bubbles,
there is really not much of the difference
in the second step of the process. The protein
molecules get attached to the air bubbles.
Air bubbles rise up to the top of the collection
cup. Dry foam can then be collected. However,
one of the advantanges of venturi pumps as
compared to the Lee's product is that there
is a good current flow into the chamber and
so in general you do not worry about the
greasy material built up on the inner surface
of the contact chamber. This helps you to reduce to times to clean
the inside of the skimmer, which can be painful
since you need to shut off your system for
a while (assuming that your system has a
valve that allows you to block water entering
the skimmer).
Another good thing about this product is
that there is an exhaust pipe going back
to the basket - the section that has a soft
rubber sponge. This sponge can eliminate the excess air
bubbles that have not been used up in the
skimming process. If this sponge does not exist, you will
see a lot of air bubbles pumping into the
tank. This sponge takes care of this awkward
situation. So you can connect the exhaust
pipe directly back to the tank if you choose
to do so.
However, the drawback of this skimmer is that this
pump can be very noisy. This is actually a common question that
you should always look into when purchasing
a venturi pump. All venturi pumps operate
on the same principle as vacuum cleaners.
It sucks air into the pump and mix the air
with water to produce the air bubbles. Because
of this reason, this pump may not be suitable
if you want your tank to be loacted in a
quiet room.
The next thing that we would like to introduce
is a very common protein skimmer manufactured
by the famous Aqua Medic Company. On the
left, you see a picture of the Aqua Medic
turboflotor 1000 unit. This protein skimmer
has a few special features that have been
patented by the Aqua Medic. We will look
at these special features closely and compare
them with the criteria listed above to show
why this is a very popular unit.
The turboflotor unit is manufacturered in
Germany and is capable of handling 125 to
250 Gallons. This unit, unlike the simple
Lee's product shown before, has an external motor (the bottom left) to drive the water (and
air) into the skimmer. That is, it is a venturi
protein skimmer.
If fully assembled, the plastic pipe is to
be connected between the motor and the grey
nozzle, the inlet to the skimmer. Water will
first enter the motor and then "processed"
before entering the skimmer through the inlet.
The motor has another inlet (not shown) for
an air pump to be connected. Inside the motor,
there is a needle wheel, one of the patented key features of the
turboflotor. The needle wheel is driven by
the motor and is constantly rotating. When
the wheel is rotated, the rotation allows
the air entering to the motor to dissolve
into the current. The significance of the needle wheel is that
rotating the wheel with many fine needles
on it forces the water to go around the needles,
and hence, more water surface is produced. This increase in water surface makes it
very effective in generating fine air bubbles.
This makes the skimmer work more efficiently
than the simple Lee's skimmer. In fact, many
American products try to duplicate this feature.
But the difference is that their wheels are
paddle wheels, not needle wheels. This makes
a big difference in performance because the
paddles do not force the water to go around
them the way the needles do. Hence the paddle
wheels do not give the fine air bubbles as
the needle wheels do. This automatically
gives a good rating on the quality of fine
air bubbles to this Aqua Medic unit.
Remember that with the Lee's product, the
fine air bubbles, the carrier of the waste,
are generated by an air-stone. You can easily
image that you will need a bunch of air stones
to produce enough air bubbles once the skimmer
exceeds a certain level of capability. So the simple skimmers that rely on air stones
are only suitable for small tanks. This illustrates the absolute advantage
of the venturi protein skimmers as compared
to the air-stone skimmers. The venturi skimmers
do a much better job than the simple air-stone
skimmers in supplying the amount of air bubbles.
Compared to the Big Mombasa, we say that
the needle wheel is one of the features that
makes the turboflotor 1000 unit a much better
choice.
The turboflotor 1000 unit is a very popular
equipment in our store. This and the following
picture are taken from two of our different
systems. The tank on the left is the same
one that we use to demonstrate different
lighting systems - Phase IV, Power Compact
- on the MoreLighting page.
The collection cup has just been cleaned
before this photo was taken. The collection
cup should be cleaned regularly.
The following picture shows the whole setup
of a Aqua Medic Reef 500 system. The Reef
500 is a complete biological filteration
sytem and it includes a Turboflotor 1000
unit. If you are considering a biological
filteration unit, this is really an excellent
system. (We will talk about this system in
the new page about Biological Filteration.)
Each of the 2 skimmers is placed inside a
sump. Pay attention to the shape of the Foam
Raiser Tube. You see that the Foam Raiser
Tube, the tube inside the collection cup,
has a unique shape. The Foam Raiser Tube
has a shape of an inverted-cone.
This inverted-cone shaped Foam Rasier Tube
is indeed another advantage of this product
as compared to the other American products. In order for you to appreciate the significance
of this special shaped foam raiser tube,
you need to know a bit more of the types
of foams that are produced inside the skimmer:
normal and protein foam.
Normal foam is produced whenever water is
being whirled up and aerated. They break
up quickly and settle down easily. Do you see the foam in the middle of the
Foam Raiser Tube? The top portion of the
foam is brownish, but the bottom portion
of foam is white. At the bottom of the foam raiser tube, the
white foam is the normal foam. Above the
normal foam is the brownish foam or the protein
foam. We know that only the protein foam
is what we want to collect.
The inverted-cone has such a shape that it
reduces the surface area gradually as the
foam reaches the top of the foam raiser tube.
This increases the probability of the protein
foam (also called the dry foam - because
the foam is dehydrated) will reach the top
and will be collected outside the Foam Raiser
Tube. The way the protein foam to be collected
is based on the fact that the heavier foam,
the normal foam, will not make it to the
top because of its weight. Gravity simply
pulls the heavier wet foam back down. On
the other hard, the dry foam, because of
the electrically charged nature, can easily
get attached on to the inner surface of the
raiser tube. Once the dry foam gets attached,
it can make its way up to the top of the
raiser tube by constantly being pushed up
by the upcoming dry foam. Once the dry foam reaches the top of the
Foam Raiser Tube, the dry foam will be collected
because the foam is not as heavy as than the wet foam (because
of the water molecules). The dry foam will be collected in the volume
outside the Foam Rasier Tube and inside the
collection cup. So immediately we see that
this skimmer is a lot more efficient than
the simple Lee's product and the Big Mombasa.
It handles most of the problem of sorting
the dry foam from the wet foam. For these
two features, the needle wheel and the inverted-cone
shaped Foam Rasier Tube, we highly recommend
this unit to people who are considering of
upgrading their skimmers.
Note: It is this special feature of the Turboflotor 1000 unit inspires us to come up with the Dry Foam Collecting Efficiency criterion in order to compare different products. So you see the these criteria that we have listed here really comes from our daily experience and from our own experiments with different products. It is not hard to see and it is nothing but common sense.
To the left is the Aqua Medic Turboflotor
5000 SHORTY. It is the latest member of the Aqua Medic
Turboflotor family. It just arrived our shop about 1 week ago.
Its operating principle is identical to the
Aqua Medic Turboflotor 1000 product. However,
this is much more powerful than the Turboflotor
1000 product. It handles 500 Gallons, whereas
the 1000 model handles only up to 250 Gallons.
Compared to the Turboflotor 1000 products,
this unit is almost 3 times as big as the
1000 unit. The external motor that mixes
the air with the water is a lot more powerful
than the one used by the 1000 unit. Perhaps
more importantly, the collection cup of the
Turboflotor 5000 SHORTY is a lot more bigger
and longer then the 1000 unit. The bigger
the collection cup, the more waste it holds.
The longer the foam raiser tube, the better
the dry foam collecting efficiency. As we
have explained a minute ago, this is because
it is now a lot more harder (the new foam
raiser tube is now twice the length of the
1000 unit) for the wet foam to get to the
top of the collection cup. This again is due to the fact that the wet
foam is heavier than the dry foam. The gradual
decrease in the opening of the raiser tube
allows a much smaller chance for the wet
foam to reach the top and hence boosts the
product's efficiency.
You may also notice that this SHORTY unit
has a much wider diameter than the 1000 unit.
It is roughly 3 times wider than the 1000
unit. This may seem a bit strange at the
first sight. Remember that we always want
a maximal air - water contact time and so
for most of the protein skimmers, the contact
chamber is usually as long as the manufacturer
can make. However, this SHORTY product goes
in a slightly different direction in that
instead of having a long tube, it has a much
wider diameter. The wide diameter allows the air bubbles
to spread out inside the contact chamber
which compensates the shortening of chamber.
Note: You can see on this picture that there
is also a small plastic air tube connecting
to the motor. The motor uses this little
tube to suck air in and generates the air
bubbles.
As far as this discussion goes, the Aqua
Medic Turboflotor 5000 BABY is the best protein
skimmer that we recommend to the advance
people. This BABY is capable of handling
1000 Gallons or twice as much as the 5000
SHORTY.
The operating principle of this skimmer is identical to all the other Turboflotor members. But this is the best skimmer shown here because it has all the features of the 5000 SHORTY and it has one more. This 5000 BABY has the same diameter as the 5000 SHORTY, but twice as tall as the 5000 SHORTY. The 5000 SHORTY is only 2 feet tall and this 5000 BABY is 4 feet tall. This approximately doubles the air - water contact time of the 5000 SHORTY.
Note: The 5000 BABY shown is 4 feet tall. There is in fact another very similar product which is the 5000 Twin that is 8 feet tall. However, the 8 feet was sold on the same day it was shipped to our shop and so we cannot include a picture here.
Since the Turboflotor family is such a popular item, we would like to discuss the 3 specific maintenance tips of this line of products.
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