First, aquarists that have fish-only systems are going to focus on higher protein concentrations than reef-keepers in general. Those reefers that have sizable fish loads along with their inverts and corals will also want to target higher protein removal. Although it is common practice to do voluminous water changes in fish systems, reef tanks rarely require water changes above 5 to 10% per month if utilizing live rock and/or live sand as primary biological filtration. Naturally, the issue of water exchanging is a matter of personal choice and preference. I mention it purely to illustrate a point. The point being: As a rule, reef tanks are maintained to more exacting tolerances than fish systems.
Maintaining a system that is as nutrient-free as possible is the dictum of most reefers. Fish tanks usually are family affairs with everyone wanting to "feed the fishies". Bleaching of dead coral heads and other in-tank decorations is an area unknown to the reef aquarists so other means of cleansing the water and the system are required. Enter the protein skimmer. I gave a brief background summary in my last article on this subject so I will forego that here. Mainly, I wish to state that not all skimmers are right for all systems.
Since I love analogies, let's use the automobile. All cars have 4 wheels and get you from point "A" to point "B". How they get you there is the issue. Just as you wouldn't drive your Cadillac into the woods to go camping, (you don't, do you?) nor would you want a tower skimmer on a 29 gallon aquarium!