What is a protein skimmer? Its a type of mechanical filter used to remove organic material from aquarium water before it can break down into phosphate and nitrate. Marine and reef aquariums frequently contain high levels of organics—much higher than you would find in an ocean reef. Protein skimmers remove these organic compounds that otherwise would have adverse effects on water quality, causing nuisance algae growth or health problems in fish, coral and/or invertebrates.
A protein skimmer, or foam fractionator, is a device commonly used to remove dissolved organic compounds (DOC) such as food and waste particles from saltwater aquariums. Skimmers could be considered one of the most beneficial devices for the saltwater hobbyist.
Protein skimmers remove hydrophilic substances from water using air bubbles that are collected in a collection cup and thereby removed from the fish tank altogether. As air and water mix in the skimmer chamber, bubbles rise and take with them the dissolved organics that are attracted to the bubble surface skin.