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Written by: tHEcONCH


Skimmers are an essential piece of marine aquarium equipment, and although there are other methods of removing waste from a marine system, they are by far the best method for home tanks. Skimmers work by injecting millions of tiny air bubbles into a chamber as tank water passes through it. As the bubbles rise through the water they attract proteins and other waste and lift it out of the water into a collection chamber. By completely removing waste in its early stages of decomposition the skimmer lessens the load on the beneficial bacteria in the tank that break down the remaining waste.


Air-driven skimmers – Air-driven skimmers, or ‘Berlin Method’ skimmers, are simple tall canisters with air pump feeding an air ‘stone’ at the base. The bubbles rise up, collect waste, and collect in a collection cup at the top of the canister. They are cheap and functional so long as they are tall and the wooden air ‘stones’ required to get small enough bubbles are replaced every few weeks. They are prone to blockage, are bulky, and seldom work well by comparison to pump-driven skimmers.

Pump-driven skimmers – Pump-driven skimmers pump tank water past an air venturi (intake) which creates turbulence and tiny bubbles in the water. More advanced models use ‘needle wheels’ to create even more turbulence and cause gases dissolved in the water to form into bubbles. The bubble filled water is then pushed through a chamber where, loaded with waste, it bubbles into a collection cup. Because they pump water rather than rely on just the buoyancy of the air bubbles to work, they are far more efficient and compact, and can clean water both faster and more thoroughly. Pump driven skimmers come in three main configurations:

‘Hang On’ skimmer – A kind of pump-driven skimmer designed to clip on to the back of an existing aquarium, pulling water up and out of the tank, through the skimmer, and then return the water to the tank.

Submersible skimmer – A kind of skimmer designed to be immersed in water (usually in a separate sump)

Stand-alone skimmer – The most common design of skimmer. As they need not be installed near the aquarium itself, these skimmers can be very large and powerful because they are not constrained by limited space. They are sometimes located in a separate room connected by household plumbing, and often require a separate ‘feed’ or ‘return’ pump(s) to get water to and from the tank.


A good skimmer is one that produces a lot of very fine bubbles and keeps them swirling about in the tank water for as long as possible where they can attract waste before bubbling to the top. All else being equal, a bigger skimmer is a better skimmer. There is no such thing as ‘over-skimming’. Some newer model skimmers contain ‘bubble plates’ and other gadgets designed to increase the efficiency of the skimmer, but the basic principles hold for all skimmers.

The kind of skimmer you buy should depend upon factors like how big your tank is and what you want to keep in it and the amount of space you have available in your cabinet, but in general you want the biggest and best quality skimmer you can afford. There is little use in buying a cheap skimmer ‘to get started’ – it really is a waste of money that should go towards getting the right skimmer for your intended set-up. I recommend that you seek plenty of advice from other reefkeepers before purchasing a skimmer - it is such a critical component that you must get the right tool for the job.

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