Aquarium Decoration

Protein Skimmer for Marine Aquariums

Welcome Reader, today we are going to focus on protein skimmers for fish tanks:

What is a marine aquarium protein separator?
How does the Protein Skimmer work?
What types of skimmers are there?

Protein skimmers are supplemental filtration devices used in marine aquarium hobby.

These devices effectively remove protein and other organic waste material, helping to maintain a healthier aquarium environment.

Protein skimmers are one of the aquarium accessories that allow the primary filtration system to work more efficiently and also provide many other benefits for superior water quality and clarity.

If you want to know all the information about skimmers for marine aquariums, do not miss this article.

Protein Skimmer: Introduction

In addition to primary biological filtration, the skimmer or skimmer is one of the most important aspects of many marine aquariums.

Although it is true that there are systems that do not use Protein Skimmer, for most marine tanks, dissolved organic compounds, phenolic oils and other yellowing agents are a problem.

Only active use of a protein urea stripper can remove them.

If you intend to build a saltwater tank, you may be interested in our guide on how to build a marine aquarium step by step, there we explain what you need to know.

But what is a protein skimmer?

First of all, say that Protein Skimmers are not fish tank water filters, they have the same purpose, but the operation is very different.

A Protein Skimmer is a device used primarily in saltwater aquariums to remove dissolved organic compounds from the water before they break down into nitrogenous waste.

The protein skimmer uses an air-driven system designed to create a dense foam that removes organic matter from the aquarium.

The skimmer is the only filtration system in the aquarium that provides a way to physically remove organic compounds before they start to break down, relieving the load on your biological filter and improving the redox potential of the water.

How does a Protein Skimmer work?

A vigorous mixing of aquarium air and water within the skimmer ‘s reaction chamber generates thousands of protein-separating microbubbles.

As these microbubbles travel through the device, waste materials adhere to the surface of the air bubbles and are literally pulled out of the water.

Debris clinging to the bubbles condenses and is transported to the protein skimmer collection cup.

This active waste removal process employed allows mechanical, chemical and biological filtration to work more efficiently. If you want to know more about the types of filtration in the aquarium you can click on the previous link.

How the bubbles accomplish this needs a slightly more complex explanation.

Active waste removal

Surely you once made bubbles when you were a child. Do you remember seeing the colors of the rainbow on them?

Those pretty rainbow colors were the light reflecting off the soap film attached to the bubble.

Just as the soap got stuck to the bubbles you were creating, so does all the trash and other organic debris in your aquarium water.

In Protein Skimmers, the bubbles are microscopic and the results can only be seen after they break up and deposit their organic residue films in the collection container.

No pretty rainbow of color here, just nasty sludge riding on the bubbles in our skimmer.

How this happens in waste treatment plants has long been discovered. By injecting large volumes of air bubbles into a column of wastewater, the resulting water was much cleaner and purer than before.

This amazing process occurs thanks to surface tension.

Surface tension and protein separation

If you remember the physical law that “opposites attract”, in this case it is for the charged molecules of dirt to adhere to the bubbles, and rise together through the water column.

Once the bubbles reach the surface, they burst and deposit the debris in a collection cup.

This container prevents dirt accumulated inside the reaction chamber from flowing back down into the water column.

This process is possible thanks to the very nature of salt water. The Freshwater Protein Skimmer is simply not feasible as the technology to make it happen is simply not practical for the hobbyist.

At the end of the article we clarify this point of the urea separator in the freshwater fish tank in more depth.

Advantages of protein skimmers

We are going to see the advantages provided by these ingenious filter systems for seawater fish tanks.

mechanical filtration

Mechanical filters improve water clarity by physically trapping visible particles from aquarium water. But even if you don’t see it, the trapped waste material is still part of the aquarium’s water column.

If the mechanical filter media is not cleaned or replaced in a timely manner, the trapped debris breaks down and releases various contaminants such as ammonia, nitrite, nitrate and phosphate back into the tank.

On the contrary, skimmers totally extract organic waste from the water column. The foamy waste material contained within the collection cup is completely removed from the water column and cannot release contaminants back into the aquarium.

chemical filtration

Like protein separators, most chemical filtration is based on the principle of adsorption.

However, in conventional chemical filter media, as the residue fixing surfaces become saturated, their effectiveness decreases.

In some cases, if the chemical medium is not replaced in time, harmful chemical materials are returned to the aquarium again.

In contrast, a properly maintained protein separator provides a nearly infinite supply of debris-binding surfaces, since adsorption occurs at the surface of each bubble.

This continuous supply of bubbles perpetuates efficient waste removal without the need to replace media or the fear of contaminants being drawn back into the tank.

biological filtration

The biological filter breaks down harmful nitrogenous compounds thanks to beneficial aerobic bacteria.

Ammonia and nitrite are converted to nitrate, the less toxic compound. Although nitrate is less toxic, sensitive reef invertebrates, including corals, do not tolerate nitrate even in low concentrations.

Many saltwater aquariums do not have the right conditions to facilitate efficient denitrification that converts nitrate into harmless nitrogen gas. As a result, nitrate levels can build up to harmful levels.

Skimmers help keep nitrate levels down by slowing nitrate buildup. They remove organic waste before it breaks down and releases nitrogenous compounds.

The use of a protein skimmer is vital in reef tanks where very low nitrate levels are crucial for coral health.

Other benefits of using a urea stripper

In addition to efficient residue removal, protein skimmers also:

  • The accumulation of dirt in the aquarium water leads to other types of problems, such as cloudy water that does not allow light to penetrate. This obviously affects the marine life in the aquarium. Using the skimmer, cloudy water can be cleaned and restored to its original condition.
  • Helps maintain proper pH by preventing the acidic condition that results from carbon dioxide buildup. Dissolved organic components in the system can create unstable pH levels. These pH levels can be unfavorable for fish and other marine life. Using protein skimmer a stable pH level is achieved in the aquarium.
  • Reduces phosphate. This helps prevent nuisance algae growth. The skimmer also helps remove nitrates and other materials that could easily cause algae to grow and spread.
  • Eliminates any biological toxin released by corals, algae or invertebrates.
  • It favors the exchange of gases and increases the level of oxygen for the inhabitants.
  • Helps support a high biological load, especially when used in conjunction with a sump.
  • Removes oily surface debris to help improve light penetration into your aquarium.
  • Improves the redox index and reduces disease-causing organisms when used with an ozonator.

Design of protein separators

All skimmers have common features:

  • The water flows through a chamber and comes into contact with a column of fine bubbles.
  • The bubbles pick up proteins and other substances and carry them to the top of the device, where the foam collects in a reservoir.
  • Here the foam condenses into a liquid, which can be easily removed from the system. The material that collects in the cup can range from a pale greenish-yellow watery liquid to a thick black tar.

Regarding the shape of the device, cylindrical protein separators are common. Although cone-shaped units have been introduced in recent times.

The concept is based on the principle that a conical body allows the foam to build up more steadily through a gently sloping transition. This reduces overall turbulence, resulting in more efficient foaming.

You need to understand that each manufacturer puts their own spin on the basic design. While the options in a skimmer are vast, it is still important to understand its basic operation.

In general, depending on the design, skimmers can be classified in two ways, depending on whether they work with a co-current flow or with a counter-current flow.

  • In a co-current flow system, air is drawn into the bottom of the chamber and is in contact with the water as it rises into the collection chamber.
  • In a counter current system, air is forced into the system under pressure and moves against the flow of the water for a time before it rises into the collection vessel.

Because air bubbles can be in contact with the water for a longer period in a counter-flow system, skimmers of this type are considered by many to be more effective at removing organic debris.

Let’s take a closer look at each type of protein skimmer.

Types of skimmers for marine aquarium

Joint Stream Protein Skimmer

Basic co-stream skimmers use an open tube or cylinder with the bubble source mounted in the base.

These use the volume of air bubbles rising up the column to bring them into contact with the system water inside the chamber body.

Water is ‘drawn’ into the cylinder from below the surface of the water and once the bubbles burst in the collection cup, the ‘treated water’ simply flows back into the aquarium.

The designs of this type of skimmers can be hung from the aquarium or mounted on the sump.

Bubble size is the key ingredient to a successful skimmer, and two methods are used to create the “perfect” bubble. This feature classifies co-stream skimmers into two different types:

air stone

The original protein separation method passes pressurized air through a diffuser to produce large numbers of microbubbles. It is still a viable, effective and economic option, although new technologies require less maintenance.

The air stone most often used in the diffuser is a partially hollowed-out block of wood. Mainly lime wood is what was used to create the necessary foam and is still used today.

Wood blocks are drilled, tapped, fitted with an air fitting, and connected via air tubing to one or more air pumps supplying at least 1 cfm.

The wooden air stone is placed at the bottom of the water column. The water in the tank is pumped into the column, allowed to pass through the rising bubbles and re-introduced into the tank.

To get enough contact time with the bubble, these units need a considerable height.

Although this method has been around for many years, many hobbyists consider it inefficient for large systems or those with high bioloads.


This is another type of protein separator that uses a venturi injector to produce the air bubbles. In terms of size, this type is smaller than air stone skimmers, although it also requires a more powerful pump to drive the pusher valve.

In the quest to build a better system, The Mazzei Injector Company developed what is known as the Mazzei valve. Today all skimmers that use this method of air injection are called venturi-type skimmers.

One of the reasons many acuriophiles opt for this model is the number of bubbles it can produce. The venturi injector can produce a large number of bubbles to effectively clean the aquarium water.

These models do not use an air stone or basswood diffuser to create the column of bubbles. Instead, they use a venturi valve to supply the water to be treated and the billions of microscopic bubbles. This is achieved within the «bottleneck» design.

How does the Venturi valve work?

Venturi valves are easily recognizable and follow the same basic design. High-velocity water entering from the left is directed to the bottleneck.

The intake nozzle is located at the top of the tube, where the movement of the water creates a flow of air, which is how bubbles form inside the valve.

The foam that comes out of the valve is introduced into the main body of the skimmer where the organic products are removed.

By displacing the accessory at the bottom of the cylinder, a vortex is created and the dwell time is greatly increased.

For years, this was the experts’ choice for protein separation, and in many circles, it still is.

It is always important that this type of protein skimmer is combined with a high performance pump. Most skimmers of this type come with a spray head design to increase the amount of air that mixes with the water.

The high performance pumps that these models have are so good that they only require a little maintenance.

This method is very popular due to its compact size and high efficiency, but venturi designs are now more likely to be included in other skimmer designs than a simple venturi design.

Countercurrent Flow Protein Separator

The co-current method works, but it’s not very efficient. The problem is what we call «residence time», or the time that the water is in contact with the bubbles.

By lengthening the reaction chamber, more water can be processed and more dirt removed. The problem is that nobody wants a tube of more than a meter behind their aquarium.

The upstream Protein Skimmer is viewed by many aquarists as the most effective way to filter aquarium water. The drawback is that although they are the most effective, they need frequent cleaning and maintenance, which makes them expensive to operate.

In a counter current skimmer, water is injected into the top of the reaction tube. The bubble source and water outlet is located at the bottom of the chamber.

Therefore, the water has to pass against the wall of rising bubbles. This effectively doubles the dwell time, making the unit more productive.

These skimmers use wooden air diffusers and powerful air pumps for bubble production.

Another advantage of this type of skimmer is that it is designed to produce a large volume of foam. They offer a constant quality and volume of bubbles every time it works.

Since it uses air stones, they have to be replaced after a while. Depending on the organic load that needs to be filtered, the air stone may need to be replaced as often as every two months.

Also check the air pump membranes and replace them if they are worn. Since this model always produces the best results, it is not surprising that more and more people are buying this type of skimmer.

Many companies today market variations on this upstream design. We are going to see the most common types of countercurrent skimmers.


Among these special “bubble cutter” designs we can find:

  • The “ Pin Wheel ” describes the appearance of an impeller consisting of a disk with pins mounted perpendicular (90°) to the disk and parallel to the rotor.
  • The “ Needle Wheel ” describes the appearance of an impeller consisting of a series of pins protruding perpendicular to the rotor from a central axis.
  • The term “ mesh wheel ” describes the appearance of an impeller consisting of a mesh material attached to a central plate or shaft on the rotor.

The purpose of these modified impellers is to chop or grind the air that is introduced through a venturi device or external air pump into very fine bubbles.

The mesh wheel design is fairly new and while it provides excellent results in the short term due to its ability to draw in more air and create finer bubbles with its fine cut surfaces, it is still being developed and is likely to continue to evolve over time. a few more years.

This style of skimmer has become very popular and is believed to be the most popular skimmer used with reef aquariums today.

It has been particularly successful in small aquariums due to its generally compact size, ease of installation and use, and quiet operation.

Because the pump is pushing a mixture of air and water, the power required to turn the rotor may decrease and may result in a lower power requirement for that pump compared to the same pump with a different impeller when it is only pumping water..

The best thing is that this type of model is cheap and will also work relatively well for quite some time.


Also known as down -draft skimmers, these designs can process large volumes of water and are well suited for large tank owners.

This type of skimmer is designed differently from the others. It works by injecting high pressure water into tubes that have a foam or bubble generating mechanism and draws the air/water mixture down the skimmer into a separate chamber.

Its design uses one or more tubes with plastic media such as bioballs inside to disperse high-velocity water that is injected through the top.

When the water falls on the biological balls, it «breaks» several times in the tower of the bioballs and manages to mix the water and air in the body of the skimmer. This results in a foam that collects protein residues.

The tube or tubes are connected to a sump with nothing more than an internal baffle plate (baffle) and drain valve.

When the water reaches the sump located at its base, the water has turned into foam. The baffle inside the sump helps increase dwell time. It also allows the protein-rich foam to go up a wide-mouth tube with the collection cup on top.

This type of model needs a long run for water due to the column full of bioballs that have to be integrated into the model. This long path of the water increases the reaction time, so for the model to work correctly, a very powerful pump must be purchased.

This is the reason why this model is larger than the other types of skimmers. This was one of the first high performance designs and large models were produced which were successful in large and public aquariums.

Smaller designs that follow the same guidelines allow smaller capacity systems to benefit as well. As with most basic models of protein skimmers, individual companies offer variations on the original design.


The Beckett skimmer has some similarities to the downdraft skimmer but introduced a foam injector to produce the flow of air bubbles. The Beckett name comes from the patented mouthpiece, developed and sold by the Beckett Corporation.

Instead of using the plastic media found in downdraft designs, the Beckett skimmer uses design concepts from previous generations.

Specifically the downdraft skimmer and the venturi. The Beckett 1408 foam injector is a modified 4-port venturi. This produces a hybrid that is capable of using powerful rated pressure water pumps and rapidly processing large quantities of aquarium water in a short period of time.

Well-designed Beckett skimmers are quiet and reliable, but the powerful pumps used in these designs are larger and can take up extra space, make more noise, and use more electricity.

spray induction

This method is related to downdraft methods, but uses a pump to drive a spray nozzle, set a few inches above the water level.

The action of the spray traps and grinds the air at the base of the unit, which then rises into the collection chamber.


Suction pump skimmers are the most popular type to use in recirculating designs, although other types, such as Becketts, are also available in recirculating versions.

There is a belief among some aquarists that this recirculation increases the contact time with the air bubbles generated, but there is no confirmed evidence that this is true.

Every time the water is recirculated inside the skimmer, any air bubbles are destroyed and new bubbles are generated by the venturi valve. Therefore, the air-water contact time starts all over again for these newly created bubbles.

In non-recirculating designs, the inlet is provided by a pump that draws water from the aquarium and injects it with air into the skimmer, releasing the foam or air/water mixture into the reaction chamber.

With a recirculating design, the inlet is normally driven by a separate pump, or in some cases can be gravity fed, to receive the dirty water for processing. On the other hand, the pump that provides the foam or the air/water mixture in the reaction chamber is set separately in a closed circuit on the skimmer side.

The recirculation pump draws the water from the skimmer and injects air to generate the foam or air/water mixture before returning it to the skimmer reaction chamber, thus “recirculating” it.

The feed pump in a recirculating design typically injects a smaller amount of dirty water than other designs. It also allows for easy control of the rate of water exchange through the skimmer and for many aquarists this is one of the major draws of recirculating skimmer designs.

Because the pump configuration of these skimmers is similar to suction pump skimmers, the energy consumption benefits are similar as well.

How to install a protein skimmer

Most manufacturers ship a model that is separated into its different parts. For many aquarists it would be impossible to assemble the device without the manual. That is why the installation of the skimmer is also usually accompanied by a manual.

Depending on the type of skimmer, it may need to be installed at the back of the aquarium or in another position. Always make sure that the connections are made correctly so that there are no water leaks when using the model.

Below you can see an official video (in English) of the assembly and installation of a CoralVue CLSC-1000HOB protein skimmer:

Can protein skimmers be used in freshwater tanks?

A skimmer will not harm freshwater fish or degrade water quality, and freshwater will not harm the device.

But the reality is that it won’t do much to improve the water quality in a freshwater aquarium. So the short answer is that if you have a freshwater aquarium you don’t need a protein separator.

The reason is very simple. Sea water is quite expensive when compared to fresh water. Due to this higher cost of seawater, it is cost effective to use a protein skimmer to remove large molecules from seawater.

On the other hand, fresh water being much cheaper, it is not profitable to use this system to remove large molecules from fresh water.

In a freshwater aquarium it is less expensive to use a biofilter to remove large molecules that are broken down by beneficial bacteria and removed by partial water changes.

If you have doubts about beneficial bacteria and their importance in the aquarium, I recommend that you take a look at our guide on how to cycle an aquarium by clicking on the previous link.

But in a marine aquarium it is less expensive to use a skimmer to remove the large molecules, before they break down into smaller molecules that can only be removed by partial water changes that require expensive seawater.

Frequently asked questions about the protein skimmer

How to clean a skimmer?

It is recommended that at least every six months the protein skimmer is removed and properly cleaned so that you can continue to offer the best service.

As part of the cleaning, the first thing would be to replace the air tube. There is no point in cleaning it as it will not work efficiently after a while.

Afterwards, it is best to disassemble the skimmer piece by piece and soak it in hot water for about an hour.

Using a brush, it is recommended to rub these parts to remove any deposits of organic matter. Once you have finished, you have to rinse it with plenty of water.

Does the skimmer remove salt?

No. A small amount of salt water may be lost from the aquarium while filtering the water, but it is not enough to cause problems. You can always add more water to fill the aquarium.

Does the skimmer remove nitrate?

To remove nitrates, you have to bind them to something else. If the nitrates are consumed by microalgae in the aquarium, then it is possible to remove them by killing the microalgae.

Does the skimmer remove phosphates?

These devices are designed only to remove proteins, which are organic waste and cellulose. Phosphates come from other sources, such as tap water. Therefore, it is not possible to remove phosphates with the protein skimmer.

Does it remove algae?

It is possible to reduce the amount of algae in the aquarium water, but it will not kill them completely. You will have to use other methods to remove them completely.

Does it remove ammonia?

Skimmers can only remove low levels of ammonia. If more ammonia needs to be removed, other types of aquarium water filtration may need to be used.

Does it remove calcium?

Most hobbyists who have used the skimmer will tell you that it doesn’t help much in removing calcium. Running the device for this reason would be a waste of time and money.

Why is my skimmer not foaming?

There are several reasons why your protein separator might not foam, but not all of them mean it’s broken. It might be too big for your aquarium. Another thing could be that the device is still within its initialization period. Having a low bioburden may be another reason it doesn’t foam. Sometimes a small adjustment can cause the skimmer to start foaming once more.

Why does the skimmer overflow?

Having an excess of foam can be easily corrected by adjusting the protein separator well. It is advisable to read the manual of the model before making changes to the settings, since each brand works differently. The height of the collection cup may need to be raised to allow excess water to drain easily.

Why is it so loud?

The noise coming from the skimmer is mainly due to the pump. The pump will have to be checked to make sure it is the reason for the noise. If you have any of the parts worn out, then they will need to be replaced to keep the model running quietly.

How to silence the protein skimmer?

The noise can sometimes come from the vibration of the device. This can be resolved by placing a rubber mat under the skimmer so that the rubber absorbs the vibrations coming from the pump.

When should I turn on my skimmer?

In general, the skimmer is usually left to run all the time. Fish, bacteria, coral, and algae release slime and dissolved organics all the time. When the water is not continuously filtered, it ends up impoverishing the quality of the water.

We hope from that this guide on the Protein Separator for the aquarium has served to guide you when buying your own skimmer for the marine aquarium.

Before finishing, if you want to have a good time, I recommend this interesting article about the curiosities of fish, you will find data that will surely surprise you.

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