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Protein Skimming Basics

Introduction

Filtration is a key element of aquarium systems. It provides life support to the inhabitants by helping to maintain healthy environmental conditions. There are many kinds of filtration that fall into the general categories of mechanical, chemical and biological. Many of the freshwater filters available today like canisters or hang-on filters use a combination of filtering categories. The way a mechanical filter works is to collect waste particles from the water column and isolate them in an area where they can be removed. Typical mechanical filters use a pad, sponge, or floss media to isolate the waste.

A protein skimmer is a form of mechanical filtration used on saltwater aquariums. But unlike other mechanical filters it does not trap waste particles in an area where they are still exposed to the aquarium water. Rather, the skimmer collects waste in a chamber isolated from the aquarium water, ready for disposal. Another key difference in protein skimming is the size of the waste particles. Depending on the type of traditional filtering media most mechanical filters collect particles that are from a fraction of a millimeter to over two millimeters in size. This would include material like uneaten foods, fecal mater, pieces of sand and any particles large enough to be trapped. However, the protein skimmer doesn’t collect such large pieces, instead it operates on a molecular level.

How They Work

Protein skimming or foam fractionation, as it is sometimes called, works on the principle of adsorption. This is where one substance adheres to the surface of another. In the skimmer’s case, we have a multitude of fine bubbles moving throughout a column of aquarium water. Within the water organic molecules of waste are suspended. As the air bubble move up and down the water inside of the protein skimmer the molecules orient themselves or collect on the bubble’s surface. When the bubbles rise in the chamber they begin making contact that forms an area of foam toward the top of the skimmer. The foam is forced up the neck of the protein skimmer isolating the waste in a separate collection chamber. The water exiting the protein skimmer is striped of a large portion of the dissolved organic compounds that it contained when first entering the skimmer. The waste product, called effluent slowly accumulates in the waste cup until it is manually emptied. In addition to the organics collected, the waste cup accumulates a brine solution of concentrated salts. In some smaller aquariums the slow loss of salts will affect the specific gravity (salinity). Periodically check the specific gravity with a hydrometer and adjust salinity levels as needed.

Advantages

Protein skimmers offer a variety of benefits for the marine aquarium. Due to the large quantity of air flowing through them they are capable of maintaining dissolved oxygen levels at or above the saturation point. There is also an oxidative process that takes place with such high oxygen levels. This reduction of compounds can increase the redox potential of the saltwater, which is basically an improvement in water cleanliness.
The most beneficial use of a protein skimmer is on a reef tank or invertebrate aquarium. These aquariums harbor millions of tiny and microscopic organisms that make small waste products continuously. They are also consuming larger waste particles, breaking them down into organic molecules. The protein skimmer’s performance is based on this continuous production of molecular waste.

Marine fish tanks can be successfully run without a protein skimmer if they are set up with efficient mechanical filtration and effective surface agitation. The water movement at the surface will provide good gas exchange by encouraging oxygen to enter the water and carbon dioxide to escape. It is important that the mechanical filter be placed in an area where it is easily accessible and frequently cleaned. Because most marine fish tanks do not have the wide variety of invertebrate life that reef tanks contain creating molecular waste, a skimmer will not perform as efficiently or on a continuous basis. A protein skimmer can be added to a fish only system without any negative side effects, other than the cost. If the protein skimmer is set up with a surface-skimming feature then it can prevent an oily film from building up on the top of the water in the aquarium.

Selection

When looking for a protein skimmer for your invertebrate or reef tank, remember that it is part of the life support system of your aquarium. The contact chamber is where the waste collection takes place. Be sure it is as large as possible. Small air bubble production is best and the more the better. Look for skimmers that create a solid white mass of fine, tiny bubbles in the column. Also, select an air driven, venture, or down draft design based on the size of the aquarium, system design, and the type of animals you are going to keep. Most importantly remember that you are building the future success of your system. Determine what kind and size of protein skimmer will meet or exceed your needs, and then spend your investment dollars wisely. When in doubt or if you have questions, consult an AquaTouch staff member for further information.

Conclusion

With the advent of new technologies and in growing information, hobbyists are more successful today than ever before. Understanding both the operation and application of protein skimming will help you to make an informed decision. Then, when you are ready to purchase you will be investing in your lasting success.