Not only does a protein skimmer remove unwanted proteins/waste from your water column, a skimmer rated to your water volume is without doubt the most effective method of boosting the oxygen levels in your tank. As water passes through a skimmer it is infused with oxygen created by the venturi valve pulling air into the column reactor.
This injection of air ensures your livestock have a continuous feed of life giving oxygen at all times.
A note on new tanks – Protein Skimmers need to settle in when introduced to a new tank. Typically the skimmer creates an overabundance of bubbles that will quickly fill the cup and overflow. This can take a number of weeks to calm down.
It is very important while in this period you do NOT turn your skimmer off. Immature tanks require this vital boost of oxygen to not only for your livestock but also for the bacteria which take care of your nitrogen cycle.
A consideration with skimmers being indoors is that they can only introduce air which is circulating in the confines of the house or building in which they are situated. Some Reefers go to the extent of running a line from the skimmer intake to outside. The benefit is an increase of oxygen (compared to indoor air), which in turn means happier inhabitants.