Protein Skimmers 101








Protein Skimmers

This section will touch briefly on which skimmer to buy for which sized tank. As well as how and why they are even needed.
First thing I would like to address is size of skimmer. There are a number of people who believe the bigger the skimmer the better. This is completely erroneous when it comes to Reef Keeping. If a skimmer is too large for a tank it will actually remove vitals elements such as calcium and strontium. It will "over skim" the tank and could potentially cause long term harm by removing things that the tank inhabitants need.
Protein Skimmers remove dissolved organic compounds from your aquarium water. These are compounds that occur as the result of broken down organic materials; such as fish waste, decaying substances, and fish food. A skimmer works by creating a large amount of turbid bubbles inside of the reactor body. These bubbles, due to lack of anywhere else to go, begin to rise up the neck of the protein skimmer towards the collection cup. This frothy mixture is covered in dissolved organics, because these compounds are light enough that they attach to and rise with the foam. When these bubbles burst as they reach the the collection cup, the “gunk” is expelled from the water column into the cup, where it’s gathered. This usually results in a coffee like substance filling the collection cup.
When you first receive your skimmer and add it to your tank, the water in the collection cup might appear much lighter and more transparent; as well as extremely heavy. This is because the skimmer is new and the viscosity of the water tends to be a little higher. It usually only takes the first week or two until this over production of skimmate (foam) slows and your new skimmer is fully acclimated to your water conditions.
The general rule for protein skimmers is to purchase one that is within 25 gallons the size of your tank VOLUME; based also on bioload (more on this below). I emphasize the word “volume” because this includes everything connected to your system that holds water. Equipment such as external filtration. If you have a 125 gallon tank, and a 25 gallon sump, your tank volume is closer to 150 gallons.  Skimmer type plays a large role in the performance of the skimmer as well. Each manufacturer may use a different plumbing system or pump.
But, wait…there’s still “BioLoads”
As you’ll notice most of the skimmers on this site have “Light Bioload” and “Heavy Bioload” ratings. What this means is if you have a tank that is barely stocked the skimmer you're looking to buy should be on the Light Bioload side. If you have one that has a ton of tank members in it, you’ll be on the Heavy Bioload side.
Some Protein Skimmers you'll notice only have one size rating. The Skimmers listed with only one size rating means that rating tends to be in the Middle Bioload area. This is USUALLY the give or take 25-40% rule. For example a skimmer with one rating of up 175 gallons should do a tank that is close to 175 gallons, as long it is barely stocked, and 105-130 gallons if it is heavily stocked. Now these are just general rules based on what we have seen with no guarantees. It's difficult to put all skimmers into one rule based on manufacturer and performance level. Getting in contact with us will definitely help decide the right skimmer for your tank.
Is Your Skimmer "Broken"? Is It Bubbling Like Crazy?
This is one of the top things we address on nearly a weekly basis. Most people that buy a skimmer will end up calling us at some point trying to say it's "broken", because it's producing a tremendous amount of foam and going everywhere. This usually isn't a broken skimmer. When a skimmer does this it's due to the viscosity of the water. Until the water is returned to more acceptable conditions the skimmer will continue to overskim and fill up the collection cup extremely quick. If your skimmer starts over producing, and it's an already established tank and skimmer, it's probably caused by something foreign getting into the tank. If it's because the tank is a new, a few simple water changes can fix the problem. Again, take any advice at your own risk, but usually 2 or 3 15% water changes will lower the viscosity and cause the skimmer to return to normal. Be careful not to do too many water changes or it can throw your tank into a new cycle.
Other Benefits of Protein Skimmers
Another way that protein skimmers are beneficial to an aquarium is they also assist in fish health by lowering pheromone levels. Pheromones are produced by the inhabitants residing in the tank. By removing these chemicals, protein skimmers reduce the likelihood of parasites and diseases in an aquarium, by helping to ensure a stress free environment. Skimmers also add much needed dissolved oxygen to tanks to help keep oxygen levels stable during all hours of the day. Without this it can cause dangerous fluctuations in the water chemistry and have a negative impact on aquarium inhabitants.
To sum up Protein Skimmers are a necessity for any tank because of their many benefits. What they remove from tanks is almost everything that is too small to get caught in mechanical filtration such as filters socks or sponges (which by the way we do not recommend). Some people will claim that a Skimmer is not a necessary piece of equipment and that they may have even had success with their own aquarium without one. We however feel they are a must have after being in business for over 3 decades and using both methods.
If you still have any further questions about Protein Skimmers, feel free to contact us at or visit our Protein Skimmer Power Rankings page to see how the brands we sell stack up against each other.