Protein skimmers are an iconic part of saltwater aquarium keeping. They're unique filtration devices that use air bubbles to clean the aquarium by pumping bubbles and water into a chamber where waste particles attach to the surface of the bubbles. As the bubbles rise in the reaction chamber, they eventually pop
—releasing all of the waste that was trapped on their surfaces. The waste that was attached to the bubbles is collected in a cup so that it can be dumped out and removed from the aquarium (at the end of the article is a more scientific explanation for this process).
If you have a saltwater aquarium over 30 gallons you should use a protein skimmer. They're superior to canister filters and power filters, reasonably priced, and they require little maintenance.
Protein Skimmers Are the Best Filtration For Larger Saltwater Aquariums
A protein skimmer is not absolutely necessary to keep a saltwater aquarium, but we still recommend it in most cases. They'll remove as much as 40% of dissolved organics, which can mean 40% fewer water changes. They also oxygenate the water very well, produce better water clarity, and uniquely remove waste before it has a chance to turn into the toxic nitrate and phosphate that most aquarists struggle to keep under control.
One instance where we might not recommend a skimmer is for small nano and pico aquariums. It is very difficult to design and manufacture small protein skimmers. For aquariums 30 gallons and under you will need a very small protein skimmer. These small skimmers are much more difficult to adjust than larger skimmers and they are never as effective as a larger skimmer. For small saltwater aquariums, it is often easier to simply increase the frequency or size of your regular water changes rather than add a skimmer. If you have a saltwater aquarium larger than 40 gallons, we always recommend a protein skimmer.
Unfortunately, protein skimmers do not work with freshwater aquariums. Protein skimmers require a high density of saltwater in order to make fine air bubbles. Without the fine bubbles protein skimmers are so ineffective that they are not worth using.
Protein Skimming Removes Waste Instead of Just Trapping Waste
With other types of filters, you are not actually removing waste. Instead, you are holding the waste in some kind of filter media, and then pumping aquarium water through the trapped waste. Only when you clean the filter and wash or replace the media, are you actually removing the trapped waste from the water. For many people, you may only clean out your filter once per month. With a protein skimmer, the waste is removed from the water and transferred to the collection cup. This is a huge advantage of the protein skimmer. It is the only form of mechanical filtration that actually removes nitrates, nitrite, ammonia, and phosphate.
Protein Skimmers Are Made For All Types of Salt Water Aquariums
There are protein skimmers that can hang on the back of aquariums, sit in a filtration sump, sit in the chamber of an all-in-one aquarium, or sit inside the main aquarium display. Protein skimmers do not use any filtration media and do not require any replacement parts other than ones that you might break or lose by accident. This means that you will save money when compared to other filtration methods where you will need to continually purchase new filter media.
They're (Pretty) Easy To Set Up
When you first set up your protein skimmer you will need to adjust it to get it skimming properly. There are several ways of adjusting a skimmer. Some use a water level adjustment, some a pump speed adjustment, and some an air inlet adjustment. The goal of adjusting the protein skimmer should be to get a relatively dark coffee-colored liquid in the skimmer collection cup. Lowering the skimmer water level, slowing down the pump, or reducing the amount of air will lead to a darker liquid. Raising the water level, speeding up the pump, and increasing the amount of air will all lead to a lighter liquid. When first tuning a protein skimmer it may take 1-2 weeks to get it dialed in. During this time, you will want to check the skimmer every day to see what is collecting in the cup, and then adjust accordingly to make the liquid lighter or darker. Once you are familiar with the skimmer, you will be able to readjust the skimmer in only a couple of minutes, and you may only need to readjust the skimmer every 1-2 weeks.
They're Easy To Maintain
When your skimmer cup is full of skimmate (skimmate is the word for the nasty-looking crud that accumulates in the skimmer cup), you will need to dump out the liquid and clean the cup. We recommend cleaning the cup once a week, even if it is not full. As the neck of the skimmer cup gets gunked up it gets harder for the skimmer to collect waste, so cleaning the skimmer cup will help your skimmer perform better. To clean the skimmer pump, remove the pump and take it to a sink. Dump out the liquid and use a sponge or algae pad to wipe down the skimmer cup, especially the skimmer neck, and then replace the cup on the skimmer body. This should only take 5-10 minutes.
About twice a year, you should do a deep cleaning of your skimmer. Remove the skimmer from the aquarium and rinse it under a sink while wiping off the surfaces of the skimmer. Remove the pump and submerge it in a solution of citric acid overnight. After the pump has soaked in the acid give it a rinse. Re-attach the pump to the skimmer and return the skimmer to service.
How Protein Skimmers Work—The Longer Scientific Answer
Waste compounds in aquariums are often polar molecules—they have two sides with different electrical charges. One side is hydrophilic (attracted to water) and the other is hydrophobic (repelled by water). As a consequence of this, a lot of the dissolved waste can collect at the surface of the water where one side of the molecule can touch the air and the other side can touch the water. Think of the oil-like scum that you can see on the surface of a dirty pond or aquarium.
Protein skimmers use an open-top tube filled with bubbles, with a cup over the open top. The waste molecules are attracted to the bubbles because there is air inside of the bubbles and water outside of the bubbles. As the bubbles rise to the top of the tube they pop and release all of the waste on their surfaces. The waste is collected in the cup.