What are you running now for filtration? In my opinion, a skimmer is a great thing to have but not totally needed on such a small tank. I've run or am running a 29g, 20g, and a 29 cube with no skimmer. It's all in the water changes and feeding which can dictate if a skimmer is needed.
The extra water volume would be nice to have as well with a sump but youre looking at some $$ to set one up. You'll need an overflow or drill the tank, the return pump, skimmer and the sump itself.
180g Reef - 60g Rimless Reef -90G FOWLR- 125g Malawi Cichlids- 40b REEF- 34g Fresh Planted-working on- 20L FOWLR- working on
I have a mix of many different saltwater fish amongst my tanks, but I love my Tangs most of all.