What is a Protein Skimmer?

A protein skimmer is a type of mechanical filter used to remove organic material from aquarium water before it can break down and create nitrate and phosphate. Marine and reef aquariums frequently contain high levels of organic material/waste because it is an enclosed ecosystem—much higher levels than what you would find in an ocean reef. Protein skimmers remove these organic compounds that otherwise would have adverse effects on water quality, causing nuisance algae growth or health problems in fish, coral, and/or invertebrates.

So where do these organics in your aquarium come from? A few examples are animal waste, uneaten food, excess bacteria, and toxins from corals and other organisms. It should also be noted that protein skimmers can also remove select additives and medications from the aquarium water too. This is important to note when dosing your tank and always check to see if the manufacturer recommends turning off your protein skimmer while dosing or feeding the tank. 

The protein skimmer diagram above is a classic internal protein skimmer, which is designed to sit inside the sump of an aquarium system. This particular internal skimmer design makes up a large majority of the skimmers used on home aquariums. 

Types Of Protein Skimmers

While there is a variety of different types of skimmers available, we can capture or organize most of them into three different categories based on how they are installed.

Hang-on protein skimmers (a.k.a. HOB skimmers): These skimmers are designed to hang off the back or sidewall of an aquarium.  

Recirculating/external skimmers: These skimmers can be mounted externally and don't need to be submerged. These are unique in that they require two pumps; a feed pump to move water into the skimmer and the recirculation pump to create the foam. While all of the external skimmers we stock here at BRS use the recirculating approach, there are other external skimmer designs out there but they are just not all that common anymore. This would include classic spray injection, Becket, and downdraft-style protein skimmers. 

Internal skimmers: These protein skimmers are designed to be submerged into a sump filtration system and are the most common design for home aquariums. In most cases, there is just a single pump that uses a venturi fitting to mix air and water together, creating the necessary foam that will skim your tank. There are also a few air-driven internal skimmers that don't use a water pump rather an air pump, but this technology is really only used for very small, nano-size skimmers. Either way, the skimmer needs to be submerged into the water to function properly which is why we call them "internal skimmers".

How It Works

Despite the differing sizes, styles, and technologies that power protein skimmers, they all essentially operate using the same exact concept. This process is referred to as "foam fractionization" in the science community. This foam fractionization process can be seen in nature on the beach where waves crash up against the shoreline creating nutrient-laden foam. The foam lands on the beach and effectively removes the nutrients from the water. 

The diagram above is drawn to represent a venturi-driven internal protein skimmer that captures 90% of the protein skimmers used on modern home aquaria.

1. Water is pulled into a protein skimmer pump from your aquarium.
2. Inside the pump, a spinning needle-wheel (or pinwheel) impeller creates the suction that pulls the water but also pulls air via a separate airline.
3. The impeller chops up the air bubbles into even smaller bubbles and vigorously mixes that air with the saltwater to create a foam.
4. The saltwater foam exits the pump into the body of the protein skimmer.
5. Organic material in the water reacts and sticks to the outside of the micro-bubbles and produces a nutrient-laden foam called skimmate that rises into a collection cup for removal.
6. Once the bubbles rise into the cup and pop, the water recollects toward the bottom of the skimmer or through a baffle system and then exit through the skimmer outlet. 

Watch BRStv To Learn More

If you would like to learn more, check out these awesome BRStv Videos which provide more in-depth information about choosing, tuning, and troubleshooting your protein skimmer!

• The best way to tune your Protein Skimmer: Learn how in just 5-minutes!
• Why most reefers are choosing these TOP Protein Skimmers of 2019!
• What do we REALLY know about protein skimmers? We’re testing to find out! | BRStv Investigates
• Is two better than one? Is a recirculating protein skimmer extra cost worth it? | BRStv Investigates
• BRStv Investigates - Does the water level in my sump really affect my protein skimmer?
• Is this wet or dry? A better way to tune your skimmer…Could the answer be air? | BRStv Investigates