A protein skimmer is a device designed to clean the water in a reef aquarium by removing dissolved organic compounds. Put even more simply, it is a controlled overflow of dirty water. Imagine a chamber that vigorously mixes air and water to create a dense foam. The cleaning action is because of the tiny bubbles in that foam. The surface tension of the tiny bubbles attracts dissolved organic compounds. As the bubbles slowly rise, a thick foam collects at the top of the skimmer and bubbles over the edge into a collection cup. By removing this foam, the water is cleaned because the dissolved organics are being eliminated before they have an opportunity to pollute the tank. Thick foam, also called skimmate, is the desired product of a well-functioning skimmer

Are protein skimmers absolutely necessary? MORE