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Skimmers - Saltwater

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Aqua Medic Turboflotor 1000, protein skimmer
Venturi sump trickle filter

Protein skimmers are also referred to as foam fractionators. They are an essential part of a saltwater aquarium, as saltwater tanks cannot be maintained without immediately removing waste materials, unlike a freshwater tank. Protein skimmers work on a very simple principle that particles suspended in water will stick to the surface tension of bubbles. The protein skimmer creates a high volume of "sticky" bubbles that rise up from the bottom of the tank. When the bubbles reach the top, they release their cargo into a cup, which prevents the material from re-entering the main tank. Waste is removed before nitrates can form!  Although several types of protein skimmer are discussed below, the venturi skimmer is the best option, as these do not clog or fail the way the skimmers powered by an airstone do.

Protein skimmer can be located in the tank, hanging on the outside of the tank or in a sump pump.  The types of protein skimmer are:

Co-Current Skimmers
A co-current skimmer places an air stone underneath a plastic tube and sends bubbles up into a cup located in the tube. An in-tank co-current will handle up to 40 gallons, but these frequently become clogged with debris that causes the motor to overload.

Counter-Current Skimmers
A counter-current skimmer draws water into the tube from a location high above the airstone instead of depending only on water drawn into the tube from below. It also has a drain tube on the cup that ensures the purified water is returned directly to the tank. The counter-current skimmer greatly increases the exposure of water material to the bubbles and is much more efficient. A counter-current skimmer will handle up to 75 gallons. The pump is usually located inside the tank, even though most of the unit usually mounts on the back of the tank.

Co and Counter Current Skimmers will require replacement of the airstone on a regular basis - usually monthly.

Venturi Skimmers
Venturi skimmers use a venturi valve to inject bubbles into the water column. A venturi valve is simply a tube with an area where the flow becomes restricted by design. The restriction increases the flow rate and reduces pressure. By intersecting a small tube exposed to the air, airflow is drawn into the restriction. When the water flow is fast enough, bubbles are created. Venturi skimmers will then have a collection area from which water will be returned to the tank. Venturi Skimmers are more expensive to purchase and will require powerful pumps, which may need to be purchased separately. For example, the Kent Nautilus requires the separate purchase of a pump that has a flow rating of 600-900 gph. Many powerheads have been modified to take advantage of the efficiency of a venturi device.

Down draft skimmers
These are also known as Environmental Tower Skimmers. Water from a sump pump is forced down a tube filled with bio balls. The water flow then takes the foam past a baffle and up into a collection area. Down draft skimmers are used in large commercial tanks.

Some of the major manufacturers of protein skimmers are Red Sea, AquaC, CPR, SeaClone, Aqua Medic, Kent, Tunze and for the higher end user - Euro-Reef.