On my 29g I have no skimmer. I just have a couple PHs with a plenum system, and a sand bed of about five inches. Also have tons of rock.
That all being said, I would go with the skimmer if you can afford it. My 29g hasn't had much trouble, but the only thing in it is a SFE (growing a bit before putting him in the 55g eel tank and bumping that eel to a 75), and they're hardy so I don't really worry much about water conditions.