Protein skimming - how they help to keep your aquarium clean and healthy.

Protein skimming, which can also be called foam fractionation or air stripping, is a mechanical process for removing waste substances from saltwater.

reef octopus classic 110ss protein skimmer rated 130g aquarium

First of all, the theory behind protein skimming is relatively simple. Molecules of many organic and inorganic substances are strongly attracted to the interface between water and gas. The attraction is a result of each molecule having a “water-loving” (hydrophilic) and a “water-hating” (hydrophobic) end. Substances that react in this way are called surface active agents. This is commonly shortened to surfactants. Surfactants include proteins, amino acids, dyes, fatty acids, albumin compounds, fats, carbohydrates, enzymes, detergents, copper ions and many inorganic compounds.

How does a protein skimmer work?

A protein skimmer creates a huge water and air interface area.  The process is initiated by producing millions of tiny bubbles in a confined space.  The surfactants become attracted to this area. As the bubbles rise naturally, an oily residue is produced at the surface.  The residue is continuously pushed up by the pressure of the foaming column until it overflows into the waste collection cup. The final stage is the bubbles burst and the liquid residue is captured.  Finally, the residue can then be disposed of.  Its color may vary from dark brown to yellow.


The impact of the skimmer bubbles.

The more bubbles there are within the interface, and the longer they are kept in suspension, the more efficient the skimming process will be. Furthermore, studies on the most advanced models indicate that up to 80 percent of all organic waste can be removed from the marine aquarium by an efficient skimmer of the correct size.

Using a Protein Skimmer while using medications.

One drawback with using protein skimmers is they may reduce the effectiveness of medications.  This is as a result of some inorganic ions (such as copper) being surfactants and are readily removed. Therefore when using medications switch the skimmer off for 12 hours immediately after each treatment. It is questionable whether the skimmer should be switched off for the duration of medication.  This is because the resultant build-up of waste products could very likely offset the advantages of treatment owing to increased stress levels to the fish.

Three Basic Types of Protein Skimmer.

The basic types of protein skimmer available are the direct-current, the counter-current, and the powered venturi skimmer.

The direct-current skimmer.

This skimmer is positioned inside the aquarium.  It is the simplest and least efficient of the designs. In its basic form, a wooden air diffuser is positioned below a hollow acrylic tube.  In addition, above this, a collection cup is placed. Bubble generation and contact time are minimal, limiting this design to the very smallest and lightly stocked aquaria. Ozone cannot be used with this model.

Counter-current skimmer.

These skimmers are is probably the most popular method in common use.  Although some designs are outdated, the unit is generally easy to install and fairly efficient. Physically it can resemble the direct-current model with the addition of an extra counter-flow feature. This keeps the bubbles inside the acrylic tube in suspension for a much longer period.  The result of this is a greater number of surfactants can be attracted and collected. Counter-current models come in several lengths.  The greatest length that will fit in a particular depth of water should always be chosen for maximum efficiency. Furthermore, it is important for both the direct-current and counter-current model to be set at the correct height in the water. The grid below the collection cup should be at the same level as the water surface.

Advance counter-current skimmer.

This type of skimmer is positioned outside the aquarium. Tank water is pumped into the top of a cylinder and mixed with the stream of fine bubbles.  These bubbles are produced from a limewood air diffuser. A counter-current effect is set up as the water exits from the bottom of the unit and the bubbles try to rise against the flow. Contact times can be very prolonged and consequently make this type of skimmer extremely efficient.

Furthermore, to prevent bacterial build-ups and nasty smells, the collection cup should be emptied and cleaned regularly. The result of this is that the liquid waste is practically odorless.

Powered Venturi Skimmer.

This type of protein skimmer is the most efficient skimming device to date.  As a result, it is also the most expensive of the three types. Such is the versatility of the powered skimmer that several designs exist.  Different designs enable positioning above, beside or inside the tank or external trickle filter sump. Hence, for a more heavily stocked aquarium, that has fish only, a larger powered Venturi skimmer is recommended.