Saltwater hobbyists often swear by protein skimmers for maintaining a clean and healthy tank. Here, we take a look at how protein skimmers work, and what roles they serve in an aquarium filtration system.
What are protein skimmers?
Fish wastes, dead plant matter, and uneaten food all release dissolved organic compounds (DOCs) that can eventually break down and release toxins. Protein skimmers are devices that keep saltwater aquaria clean by removing dissolved organic compounds from the water. In terms of appearance, skimmers are usually tall cylindrical vessels, consisting of a reaction chamber, a pump to circulate water and air, a mechanism to create air bubbles (e.g. a mesh or wheel impeller, air stones, or venturi valve), and a collection cup to catch any skimmate. Due to their height and overall size, skimmers are often housed in a sump.
How do protein skimmers work?
Protein skimmers work by continuously mixing air and water to form a dense foam that traps dissolved organic compounds. As the volume of foam grows, it eventually spills over into a collection cup that can be removed and emptied periodically. This process—separating out contaminants using a rising column of foam—is also known as foam fractionation. If you’ve ever observed foam on a seashore, then you’ve seen foam fractionation at work in nature.
To dig a little deeper into how skimmers work, consider that dissolved organic compounds include macromolecules like fats, sugars, and proteins. These large molecules may be attracted to water (hydrophilic), repelled by water (hydrophobic), or they may be amphipathic, meaning that they exhibit both properties. Because of their resistance to water, hydrophobic and amphipathic molecules tend to accumulate anywhere there is air, which may be at the surface of the water or around any air pockets. Protein skimming takes advantage of this by creating a large amount of air-water interface in the form of bubbles. To do so, skimmers vigorously mix air and water together to create and disperse air bubbles. Organic compounds and particles collect on the surface of the bubbles, and as more bubbles accumulate, they collect into a foam that rises upward in the reaction chamber while excess water drains back to the tank. Ultimately, the relatively dry foam overflows into a removable collection cup. At this point, the collected foam settles into a liquid consisting mostly of organic compounds that have been “skimmed” from the water. The cup is emptied periodically to discard the skimmate.
Benefits of protein skimmers
While protein skimmers are not strictly required for every marine aquarium, they are very popular among hobbyists—and for good reason. Skimmers offer plenty of benefits for saltwater tanks, including:
- Less maintenance. Skimmers collect dissolved organic compounds into an easy-to-clean collection cup, helping tank owners reduce the frequency and volume of water changes.
- Improved oxygenation. Compared to other aeration methods, like air stones and surface agitators, skimmers create lots of tiny bubbles through vigorous air injection and water movement. As a result, skimmers enhance aeration by creating greater surface area for gas exchange.
- Clearer water. Skimmers remove pigments and particles that can cause discoloration and cloudiness, leading to better clarity and less odor.
- Consistent water quality. Skimmers help to remove macromolecules and particles that would otherwise decay, helping to stabilize water quality and prevent spikes in ammonia and nitrite.
- Reduced algae growth. Algae feed on nutrients like nitrate and phosphate. Skimmers help to keep algae growth under control by removing wastes before they can break down and release nutrients into the water.
In general, skimmers tend to offer the greatest benefit for large tanks and tanks with high bioloads, since water changes can otherwise require so much work. Protein skimmers are also particularly popular for reef tanks due to their high sensitivity to water quality issues.
When to skip a protein skimmer
For all their benefits, skimmers aren’t cheap, with a price tag easily fetching hundreds of dollars. So before investing in a skimmer, be sure that it’s the right choice for your setup. Skimmers are generally less often recommended for:
- Freshwater tanks. The high ion content of saltwater means that organic compounds have a low affinity for water, making them more likely to cling to the air bubbles produced by the skimmer. The inverse is true in freshwater environments, where organic molecules will tend to dissolve and stay in solution, meaning that skimmers are far less effective at removing organic compounds from freshwater tanks.
- Low bioloads. Wastes take longer to build up in understocked tanks, so water changes don’t need to be done all that often. While adding a skimmer to a tank with relatively few fish won’t hurt, it will add extra expense and bulk to the tank setup without yielding much benefit in the way of reducing tank maintenance.
- Some planted tanks and algae refugia. Many hobbyists incorporate aquatic plants and/or algae refugia in their tanks as a means of maintaining good water quality. This is because plants take up certain compounds, like nitrate and phosphate, that can be harmful to fish if allowed to accumulate. But since protein skimmers remove organic compounds before they have the chance to break down, they can sometimes deprive aquatic plants and macroalgae of the nutrients they need to thrive. For this reason, skimmers may be counterproductive in tanks that already do well at keeping nutrient levels low.
Can a skimmer replace biological filtration?
Biofilters and protein skimmers can work together to keep aquarium water clean, but a skimmer is not a substitute for biofiltration. Where the job of a skimmer is to remove small particles and dissolved organic compounds, the primary aim of biofiltration is to break down toxic wastes like ammonia and nitrite. These compounds are very soluble in water, so they can’t be removed through either foam fractionation or mechanical filtration. Instead, biofiltration works by harnessing beneficial bacteria to break down ammonia and nitrite and convert them into the less toxic compound, nitrate.
Even though protein skimmers can’t directly remove ammonia, they do help to enhance biofiltration performance in a few ways. Firstly, skimmers help to prevent ammonia from entering the water by removing organic macromolecules and small particles before they have a chance to break down. This helps to reduce the overall load of wastes to be broken down by beneficial bacteria in your biofilter media, which in turn makes for healthier nitrogen cycle, and more stable water quality. Additionally, skimmers help to aerate the water, increasing the availability of oxygen that is critical for aerobic microbes to consume wastes.
Using MarinePure® biofilter media with a skimmer
MarinePure® biofilter media offers some unique design advantages, including a continuous pore structure that supports a skimmer’s high flow rate, and a large amount of surface area for exceptionally efficient biofiltration performance. Additionally, since MarinePure® is available in a variety of shapes and sizes, it provides ample flexibility for use in tanks, sumps, canister filters, or HOB filters. The MarinePure Vault can also be used as a riser for a protein skimmer, helping you to achieve the optimal depth for your skimmer while also securely retaining your biofilter media.
If you’d like to try MarinePure® with your skimmer, just click on over to our website for more information or reach out to us with your questions. We’re here to help you achieve a cleaner, easier-to-manage aquarium with advanced biofiltration media.