What’s a protein skimmer?

A protein skimmer looks like a freak experiment gone wrong, if you’ve ever seen one. In a very brief sense, it’s a series of 3 components put together in order to filter your aquarium’s water. All protein skimmers consist of at least 3 things:

1. A collection cup
2. A body
3. An air source

They’re made to filter the water by trapping organic molecules, such as proteins and amino acids. They “trap” these molecules with air bubbles, generated by mixing the water in your tank via an inlet hose, mixing the water with air in a reaction chamber, and then releasing the filtered water through an outlet- probably a return hose to your reef or aquarium.

Have you seen the foam on a sandy shoreline at the beach? That’s exactly what a protein skimmer mimics, but rather for your reef. The skimmer generates foam, which inches upwards and pours into a collection cup. The foam is actually all the organic molecules that have been filtered from your water. This consists of fish waste, food, nitrites, salt, sugar, ammonia, most amino acids, and most inorganic compounds. Protein skimmers can even remove fats and oils from your water as well.

Different brands make different skimmers. Reputable brands such as Reef Octopus, Coralife, AquaMaxx, and SC Aquariums are all brands I trust and work with in the lab. I’ve written reviews on each of them that you can check out if you’re interested in those particular brands.

How does a protein skimmer work?

It’s simple, but complicated. Basically, here are the steps of how a protein skimmer works for the most basic design:

1. A protein skimmer takes in your reef’s water through an inlet
2. The water goes into the reaction chamber
3. The water is then mixed with air by either an air pump (most common) or venturi system (less common)
4. The mixture allows all the dirty stuff from your water to be trapped by air bubbles
5. The air bubbles slowly float to the top and form a foam
6. As the reaction proceeds, the foam collects into a collection cup at the top of the reaction chamber
7. The foam condenses into a liquid, usually darker in color compared to your reef’s water
8. The cleansed water exits the reaction chamber via an outlet
9. The cycle repeats

Ideally, you’d want water to remain in the chamber for at least two minutes for maximum effectiveness. Calculating this is hard, so think of it as getting the all of the water in your tank to cycle twice per hour. Look at the manufacturer’s pump rating and calculate it according to your tank’s volume. For example, if you have a 700 gallon reef system, you’d want a 350GPH pump, preferably a little higher.

Why do I need a protein skimmer?

Protein skimmers are often avoided because many reef hobbyists can simply do fine without them. However, that’s only to say until they have a sudden algae outbreak. Followed by another. And another. Until finally they have to tear down their tank to rid all the algae and other nasty stuff. That’s not to say that every aquarist can’t have success without a skimmer, in fact, many do. In fact, Coralife states that a protein skimmer is a necessary component to any reef.

A protein skimmer is a necessary and vital component to mimic the true effect of a reef habitat. In nature, the ocean acts as the protein skimmer for all marine inhabitants. When you take a piece of that ocean and throw it into a contained environment, it’s not the same using an air pump, canister filter, and wavemaker.

By neglecting the skimming, you’re throwing a small, but natural and necessary, part of the ocean. It can be a pricey investment, but think about all the benefits it provides along with the peace of mind you get from sudden algae outbreaks.

It’s commonly believed that even the cleanest tank on the planet isn’t even 1000x as clean as the ocean. I fully support this belief. Your reef tank is dirtier, will be dirtier, and will always be dirtier than the ocean. That is, until we can make a superfilter. Sorry if I just burst your bubble.

But, you can compare your setup to other reef enthusiasts. If you have a protein skimmer, you’ve already proven to yourself and to others that you actually care about your setup and you’ve got your bases covered. Plus, a skimmer is one of those things that even hobbyists know a little about (which is probably why you’re reading this too). Imagine if you had guests over or you showed off your reef online, along with your skimmer. That gives you a lot of credit and shows dedication towards the hobby. Some skimmers have an excellent reputation behind them, such as Coralife, which makes amazing protein skimmers.

Whether you do it for pride or for the reef, a protein skimmer will be one of the best investments you can make. It’s kind of like car insurance. You *could* go without it, but when you need it, you’re screwed.

Although most skimmers are pricey, which is the main obstacle, I’ve worked with some that are powerhouses and are very affordable in pricing. Reef Octopus makes a lot these. Check out my review here.

The different types of protein skimmers

There are many different variations of skimmers on the market today. But they can all be grouped into two main categories:

1. Co-current flow
2. Counter-current flow

Co-current protein skimmers

These skimmers basically function by pushing water in from the bottom of the reaction chamber and forcing the water up, along with air, from the bottom. Air and water flow in the same direction and thus, it’s co-flow. This type of model is usually powered by an air stone or venturi pump, otherwise known as an aspirator. Air stone powered systems remain an efficient and effective means of skimming, although newer systems are available. The air stone is usually a block of wood with fine holes. The best protein skimmers maximize air and water mixture, thus this type of model is usually very large and tall.

Venturi systems are pretty much outdated now. They work by forcing water through a tapered hole with an air inlet. This model is inefficient and slow. I won’t comment much more on this and don’t recommend any products that uses a venturi air source.

Counter-current protein skimmers

The most popular models on the market today that are proven to work use counter-current modeling. I also highly recommend this over co-current skimming, as I’ve worked with both and counter-current produces much more noticeable results compared to co-flow. If you’re in the market for a skimmer, consider going counter-flow, especially if it’s your first skimmer. These skimmers are a lot easier to use and much more efficient. Coralife and SC Aquariums both make excellent counter-current skimmers. I have reviews for the most popular skimmers by Coralife here, and SC Aquariums here.

The most popular model is the aspirating model. This uses a pin-wheel design that basically consists of fine needles on a disk at 90 degrees. So think of a platter with sharp needles going straight upwards from it. On the bottom of that platter, there’s a rotor that spins. The point of this model is to chop or shred the air into extremely fine bubbles, and then mix it with water. There are basic variations of this model, the top three being:

1. Pin-wheel
2. Needle-wheel
3. Mesh-wheel

The pin-wheel is basically an impeller with needles on a disk, as described above. The needle-wheel is the same concept, however the needles project outwards from a central axis.

The mesh-wheel is relatively new, and consists of no needles at all. It’s a piece a mesh attached to a central plate and generates bubbles through its fine mesh material. This model has been regarded as extremely efficient for reef systems that are smaller in size, along with the ability to be easy to setup and use as well as quiet operation. In fact, many DIY-ers tend to model after this concept as it’s proving to be the most efficient. Many models of protein skimmers now use the mesh-wheel design.

Now that we’ve covered the designs of skimmers, we can get to the other variances.

Next, we’ll cover the three placements of skimmers.

In-tank protein skimmers

This type of skimmer is convenient because it can be placed directly within your fish tank. It has all the basic functionality and equipment, with a motor pump at the bottom. SC Aquariums and Coralife both make excellent standard skimmers.

Pros:

• Compact
• Generally cheaper
• Easy to setup and good for beginners

Cons:

• Ugly
• Needs to be hidden
• Can be noisy

Hang-on-back (HOB) protein skimmers

HOB skimmers are relatively new to the market, but were disregarded when first introduced. They were known to be inefficient and noisy, as well as useless due to their small size. Now, modern HOB skimmers have improved and some models even match up to the big boys. HOB skimmers are generally cheaper and come in a variety of makes and sizes. AquaMaxx makes my favorite skimmer, and I wrote a review about their HOB here. Reef Octopus makes another alternative, which you can read about here.

Pros:

• Takes up no tank space
• Can easily be hidden with a background
• Cheap

Cons:

• Noisy
• Selecting a model can be difficult (see my recommendations for the best performing HOB skimmers)
• Ugly if in sight

Recirculating protein skimmer

These skimmers basically recycle the water multiple times within the same skimmer. The goal is to cleanse the water not once, but usually multiple times before being return to the sump of the aquarium. Aspiration is the main model recirculating skimmers use, as well as some other designs- such as the Beckett design. There’s been controversy over this model where re-circulation increases the contact time of the generated air bubbles, but no official proof. When water is reintroduced within the skimmer, all bubbles within that water are ridden and new bubbles are formed. Thus, the water is only in contact with newly introduced “clean” bubbles. This type of model usually has two pumps- one to pull water in, and another to provide the water/air mixture in a separate cycle tube. The cycle pump pulls water out of the skimmer and adds air into the mixture before introducing into the reaction chamber.

Surprisingly, the cycle pump injects a less amount of dirty water than a co-flow or counter-flow design. This is because the separate pump allows you to control the rate of water intake through the skimmer. In a traditional co-flow or counter-flow design, dirty water is easily taken into the chamber, as you have no control over this. In a recirculating skimmer, you can control how fast the water is removed and re-injected back into the chamber. If you increase the pump GPH, water is cycled faster and cleaner each time it’s injected back into the chamber.

In a counter-flow or co-flow chamber, dirty water entering the system is 100% dirty.

In a recirculating protein skimmer, water is 100% dirty upon first injection from your reef tank. After it enters, it’s cycled, then re-injected again. This time, at a much lower percentage than previously entering the system. Then, another cycle occurs. Now it’s even cleaner.

This is a sought-after feature and is very beneficial to your ecosystem.

How to choose the best protein skimmer for your tank

I’m here to help you choose the best protein skimmer for your setup. To choose the right skimmer for your reef, I suggest you ask yourself these three questions:

• How much space do you have for a skimmer?

If you have little-to-no space, I suggest you go for an in-tank or HOB skimmer. If you have the space, go for recirculating.

• How much money do you have for a protein skimmer?

Cheap models are readily available and can perform the essential basic functions. However, if you can afford it, I suggest going for a premium model. Cheap models tend to be not as efficient and noisier. More expensive models can provide a lot more benefits compared to cheaper ones. You get what you pay for.

• How big is your tank?

If you have a large tank, you obviously need a protein skimmer with a higher-rated pump. If you have a small tank, you can easily get by with a basic skimmer with low flow rates, such as a Reef Octopus.

Of course, other considerations come into play such as your noise tolerance and electrical bill. These are other factors I review each individual skimmer, so check them out if you’re interested.

Can protein skimmers be used for freshwater tanks?

Yes, you can definitely use a protein skimmer for a freshwater tank, but it depends on your current filter and how much you care about your fish. If you have dual filters with a UV sterilizer and a canister filter, you’re probably OK. However, if you have a basic filter and want some extra protection, you should check out a protein skimmer as an extra layer of filtration. It won’t do any harm, and if you have the budget, go for it.

Other considerations

Protein skimmers are a vital component of all reef and marine setups, and is often neglected. I think many people just don’t realize the power and ability of these skimmers until they run into some trouble. Just like earlier, I said it’s like car insurance. You don’t need it until you need it. If you’re serious about corals, reefs, marine fish, or even freshwater fish, a protein skimmer is just as important as your filter, lighting system, or even fish food itself. Please, don’t skimp on something that’s necessary for your setup, just because it’s misunderstood. Your habitat will thank you.

Now that you’re educated just a little more on the matter, you probably want to find the best skimmer for your reef. Check out some reviews I’ve written. I’ve wrote a review for every skimmer we have here in the laboratory. You can see a full list of protein skimmer reviews here, along with my suggestions for each and every model.

From one aquarist to another- thanks for reading, and please share this article with your friends and online communities so everyone can become educated of the issue.