Protein Skimmers

at 5:02 pm

Many store owners and clerks may think that protein skimmers are relatively new devices–a perception resulting from their popularity among the growing reef aquarium segment of the fishkeeping hobby. Actually, protein skimmers (in one form or another) have been around at least 40 years in the United States and longer in some European countries. Unfortunately, there are still misconceptions about what they can and cannot do, as well as how they can best be utilized in an aquarium system.

What follows are a group of basic questions, the answers to which will hopefully prove useful in eliminating these misconceptions and fostering a more complete understanding of the nature and function of protein skimmers.



The difference between brands of skimmers is most evident in the ways they move water and generate bubbles. There are two basic types of protein skimmer: co-current and countercurrent. Current pertains to water flow, while “co-” or “counter-” indicate whether the air is moving with or against the water current, respectively. Either of these units will require an airstone and air pump to generate the bubbles needed for operation.

Other skimmer models employ a venturi air injection system instead of an airstone to produce bubbles without an air pump. The skimmer types pump aquarium water through an injector via a water pump or powerhead. The injector has a narrowed pathway in its center and an additional opening that admits air into the unit.

Differential pressure is generated at the other end of the restriction which causes air to be sucked into the water stream. Venturi operated skimmers can be very effective and tend to be smaller than other skimmers–a positive consideration in areas of limited dimensions.


Another misconception of foam fractionators is that they will not work in freshwater. The fact is, most units available today will function in freshwater. It is, however, more difficult for a skimmer to generate small bubbles in freshwater and it cannot do it as quickly or efficiently.

In most cases, the primary protein skimmer consumer is the saltwater hobbyist. Whereas, in the instance of a fish-only tank, a skimmer can be considered an option, in a reef aquarium it is a must. Whether your reef aquarium owner has a wet/dry filter or not, a protein skimmer is vital to maintain the lowest possible organic levels. In fact, one reef-keeping approach, the Berlin Method, relies on the protein skimmer more than any other piece of equipment.

In a Berlin reef system, the skimmer is used to remove DOC before bacteria break them down into ammonia. But there is more to a Berlin system than just a protein skimmer. Any ammonia present is removed by the organisms growing on and in the live rock that is a vital part of any reef system. Because they also require large amounts of light (of the proper wavelength) for growth, an efficient, reliable lighting system is also necessary. A fair amount of water current is also mandatory. Finally, due to the fact that the emphasis of a Berlin system is on coral, not fish, the fish population, is kept light and fed sparingly (if at all) with prepared feeds. Just as an aside, the cost of setting up a Berlin system is essentially the same as that of a wet/dry filtered reef system.


The most simple skimmers, although not that common anymore, fit inside the aquarium, hanging from the top lip of the tank. An airstone placed at the bottom of the column produces the foam which is collected at the top. This type has no water pump, no hoses. A more common version hangs on the outside back of the aquarium. Water is pumped into the unit, either co- or countercurrent, and returns to the tank via a spillway at the top. Perhaps the most commonly used type of skimmer sits on the floor (in the cabinet) next to the sump–at times in the sump. Exit water is diverted into the sump, where it is pumped back up to the aquarium. No particular placement is superior to another. Selection is usually a matter of individual space and budget restraints.

Other common questions…


The primary benefit of activated carbon is the removal of organics. Since this is also the function of the foam fractionator, does the hobbyist really need both? The answer is yes. Studies show that foam fractionation does not remove all types of organics; nor will it remove 100% of any one of them. The same can be said of carbon. The two filtration devices effectively complement each other.


Twenty four hours a day. There will be some periods of the day when the skimmer will produce more foam than others, but that is natural.


No. In addition to DOC, protein skimmers can remove other substances, e.g. trace elements. However, the substances are easily replenished.


To retain its effectiveness, a protein skimmer must be clean to allow the bubble to form at the top and flow to the collection cup. A short time after installation and continuous use, a greenish brown sludge will begin to form on the walls of the skimmer. This should be brushed off regularly. The airstone should be replaced each month. For a venturi skimmer, the venturi should be cleaned often to prevent the build-up of calcium or other deposits.

Related Post

Leave a comment

Your email address will not be published. Required fields are marked *