Air Driven Counter-Current Skimmers

The Basics Components and How They Work

From our discussion about that protein skimming is and how it works we outlined the three basic styles of protein skimmers used in saltwater aquarium and reef tank systems; air driven counter-current (CC), venturi, and downdraft or E.T.S units. In this article we are going to take a closer look at the basic components of air driven CC skimmers and what makes them work.

The Basic Components

• An air driven counter-current skimmer model.
• An air pump, which needs to be large enough to provide an adequate force of air through a sufficient number of air stones to insure that the skimming water column is that of a milky white appearance.
• Air stones, preferably good quality imewood stones.
• Depending on the model of skimmer you buy, a water pump or powerhead.

Using this photo that we took of our Lee's Aquarium Air Driven CC Skimmer, (read full review), we have labeled all of its basic components to give you a general idea of how this style of skimmer is set up, which uses an air pump that is not shown. This particular model is designed for in-tank use. Other similar models made are the Red Sea Berlin Air-Lift and Classic, Aqua Medic Midiflotor and Turboflotor 750, just to name a few (read reviews & compare prices). There are also CC skimmers designed for hang-on-tank or in-sump mounting, many of which combine counter-current with venturi style skimming. These models use a water rather than an air pump to drive them (read reviews & compare prices). Whichever type you decide on, the basic principle of how they work is pretty much the same.

How These Units Work

• Water is fed into the skimmer chamber (uplift tube) usually by means of an air supply, water pump, or can be gravity fed by using a water surface overflow set up. For our Lee's in-tank model the water from the tank is drawn into the uplift tube through a small hole near the top of the tube, just below the aquarium water line.

• Air is pushed down through the air stone by means of the upward air flow supply hose and adjustable valve, in turn creating the very fine bubbles that rise in the uplift tube, which then carry unwanted microscope organics (DOC's) and other compounds to the collection cup for disposal.

• The downward air flow supply introduced into the skimmer chamber goes against the upward air flow supply allowing the bubbles rise slowly to the surface. This is referred to as "dwell time". The longer the dwell time, the better the skimming process. The skimmed water is then dispensed back in the aquarium by whatever means a particular skimmer is constructed to do so, usually from a location at the bottom of the skimmer. The Lee's skimmer bubbles the water back up into the aquarium, which is drawn up through the return tube in coordination of the downward air flow supply connection.

That's it plain and simple. Counter-current, meaning upward flow VS downward flow air supplies that counter balance each other to make it all work. Now let's look at the pros and cons of this style of skimmer.

The Pros

• Fairly easy to put together and install.
• Fairly inexpensive to set up.
• Requires very few pieces of extra equipment to buy.
• Usually compact, not as bulky as some other styles of skimmers.

The Cons

• Air stones may require frequent changing.
• Making sure you choose an adequately sized skimmer to meet the skimming demands of your system. If too small you may have to add an additional skimmer, or buy a different one all together.
• By not choosing an adequately sized air pump, one that is strong enough, you may have to buy a different one later on.
• In-tank set ups may get in the way of other equipment; i.e. canopy light hood, because the collection cup sticks up above the water line and aquarium frame.
• In-tank set ups may not appeal to some aquarists, because you can see the skimmer inside the aquarium.
• The taller the skimmer chamber the more the air bubble dwell time increases, but in-tank set ups can limit the height you can have.
• Hang-on-tank set ups can be mounted behind the aquarium more out of sight, but only if you have the room, and can be limited on skimmer height as well, because most likely you don't want an ugly tube sticking up behind your aquarium.
• In-sump set ups can be hidden all together under a cabinet, but do require a water pump and somewhat specialized installation and plumbing. If you have a short cabinet, this again can put a limitation on the height of the skimmer you can have.

Debbie & Stan Hauter
About Guides to Saltwater Aquariums

More About Skimmers & Skimming
What is Protein Skimming?
A Layman's Guide to Protein Skimming
Protein Skimmer Set Up Resources
DIY Skimmer Project Resources
Skimmer Supplier Resources

Read Reviews & Compare Prices
Guides Top Hang-On-Tank Skimmer Picks
Guides Top In-Tank Skimmer Picks
Guides Top In-Sump Skimmer Picks

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