What Is A Protein Skimmer And How Does It Work?

When you go to the beach and “sea” foam, pun intended, you will also smell a very familiar odor. The ocean is a gigantic system of natural filtration and chemical dosing. Today we will focus on the filtration factor. Protein Skimming!

First off, what on Earth is protein skimming and why do we need to utilize these devices? A protein skimmer uses nothing but air bubbles and water to extract Dissolved Organic Compounds, or DOCs, not to be confused with Department of Corrections. The protein skimmer is also responsible for injecting high levels of oxygen into your water. After all, we stopped using air bubbles in our display tanks years ago, most of us anyway.

The general shape of a protein skimmer is a cylinder. It usually consists of a large body, an inlet, and an outlet. On top of the skimmer is a collection cup which is where the waste, or skimmate, ends up. Some cups have a drain hose that can increase time between dumping. The means for getting water and air into the body of the protein skimmer vary but for affordable educational purposes I will use my protein skimmer for today. On my 20 gallon tank I have a Pro Clear Aquatics Systems 75 gallon rated sump that came with a matching skimmer. I would not use something like this on a 75 gallon as it is very small. For a 20 gallon tank with nothing but peppermint shrimp it works great. I always oversize where possible.

image via Spitman BostonReefers.org

This particular model is a good example because it is not much different from the main population of skimmers on the market. The pump has an air hose that sucks Oxygen into the pump where it smashes into the water via impeller. The mixed water then makes its way up through the PVC into the “Reaction Chamber” where the air makes its way up to the collection cup as the water works its way down to the outlet and back into your sump or aquarium. This particular model is an in-sump type that requires 3 inches of water to run at its best.

Now with air going up and water going down there are a few things to make sure are not happening. It is very easy to flood a house with an improperly tuned protein skimmer. Most of the time they will have a valve that controls air flow, one that controls the flow of the pump, and one that controls the internal water level of the Protein skimmer itself. Since the top of the skimmer is an open hole you have to balance the three parameters to your skimmer’s “sweet spot” which usually is marked or IN THE OWNERS MANUAL WHICH YOU HAVE MEMORIZED!

Here is a good thing to remember when tuning the skimmer: Sorry, but math is a must in this hobby.

Water + Air = Less water.

Less water = Lower Level

Lower Level = Drier Skimmate 

Water – Air = More water

More water = Higher Level

Higher Level = Wet Skimmate

This Skimmate is a medium consistency in my collection cup.

The choice is yours whether you want dry, wet, or medium skimmate. If your tank is more fish than coral a wet skimmate is what I would choose to make the fish happy. If you have a full blown reef tank, the corals may benefit from a Dry skimmate. A lot of species thrive in dirtier water so make sure you know what your corals like.

Protein skimmers come in all shapes and sizes, so you can use one on any sized tank. There are 3 main types sold today, differences being flow and water delivery.

Co-Current Flow:

These work by using an air stone in the reaction chamber or by having a Venturi Valve after the pump. This is the simplest form. It is called Co-Current because the water and the bubbles flow in the same direction.

Counter Current Flow:

One of the more popular and efficient designs is the Counter Current Flow. Air and water are both injected into the pump, thus getting smashed, chopped, and beaten but the impeller. Some models us standard impellers but the better quality pumps will have needle wheel or mesh. These chop the bubbles as fine as humanly possible which creates more surface area for the DOCs to bond to the bubbles during Skimming. Other methods of Counter Current are Down-Draft, Becket Style, or spray induction skimmers. These are not quite as popular but can be just as effective.

Recirculating Skimmers:

These seem to be the most efficient skimmers on the market. They require an external pump or can be gravity fed, however they have one or more pumps plumbed into the Reaction Chamber on a closed loop. This takes the foamy water to the next level and beats it to death again and again at rates much faster than an equally rated counter current skimmer.

Again, the choice is all yours. Each tank is different so you need to know what will fit your sump and budget. If you are a DIY person than you can get diagrams to make your own. If you have the blessing of a dedicated fish room and a sump with a lot of clearance you can make it as loud and big as you want! I know I did.

MarineDepot.com created this great diagram of basic protein skimming.

Basic diagram from MarineDepot.com

If you have questions or comments about Protein Skimmers or other aquarium filtration please check out our equipment forum and post a NEW topic: Equipment, Lighting, Hardware, & Filtration