I voted other. It really depends on your style of reefing and care of the tank along with natural filtration methods and nutrient uptake. Tank size matters as well i imagine. It can be needed and utilized but also not be needed for others. I personally do not use one because I rely on nutrients as the base of my ecosystem. The skimmer pulls way to much out leaving lack for the system. Others may find that they have too much nutrients and need the skimmer to pull the excess out. All on how you reef I suppose.