[Mr_X]

i know more than a handfull of people who sucessfully keep small reef tanks without protein skimmers.
you are talking fish only. i think it can be easily done, utilizing regular waterchanges as excess nutrient removal.

gases are gases. they are not a film on the surface. the film on the surface is what restricts the gases from leaving the tank. a powerhead towards the surface is a good way to fix that.

a larger tank is always easier to maintain than a small tank, but i wouldn't suggest you jump into a large complete setup without knowing if you are going to stick with it. unless you have money to burn. then i say- go with a 500 gallon display!