Andy,
You seem to be wanting to do a fish only saltwater tank - small desktop size.
It can be done - but as slowest is fastest said - not real cheap if you want to do it right.
As long as you take care of the water, bio, chemical and mechanical filtraion, you can certainly set one up. Maybe a couple of very small fish only and that's that.
Do what YOU want to do - and have fun doing it.
Brian