Protein Skimmer/Foam Fractionator
Tech Talk 78
Ammonia, feces and carbon dioxide are not the only waste products in a recirculating fish system. There are also complex organic substances from decomposing feed, urea, fish slime and metabolic by-products. Added to that are algae, phenols and saprophytic bacteria that irritate the fish's gills, affect growth rate and increase disease susceptibility. These dissolved and suspended materials make up the biochemical oxygen demand (BOD), color, odor, taste, turbidity, etc., that a foam fractionator can remove.
Foam fractionation (also referred to as protein skimming and protein fractionation) works best in salt water where foam production is easier, but it can be done and is becoming more popular in freshwater systems.
The process uses air bubbles from a fine bubble diffuser or venturi to create the foam. The foam adsorbs and entraps the above pollutants, along with the surface active compounds that make foam production possible, all of which are then expelled through a discharge tube or into a holding chamber.
The use of ozone can enhance this process. It will also aid in the control of bacteria, protozoa and viruses. In general, a protein skimmer should be sized to give a time of residence between thirty seconds and two minutes in the contact chamber. Longer periods are needed to remove smaller particles.
In general, the higher the pH and salt level, the better they work. We offer no guarantee on these and they are not returnable because we have no control over your water's ability to produce foam. Learn a lot more from the book Recirculating Aquaculture Systems (WQB109).
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