If you have a sand bed, you don't need to have a skimmer, as long as you change your water regularly and don't overfeed you rank and don't overstock. In a 29 g, you may want to keep only 3 or 4 small fish. With a pair of clowns, you can keep one or two more fish only.
I have a 24 g tank with sand and a refugium and LR. I am having a Carpet and Orchid dottyback and a Shrimp Goby. I will add two clowns, most likely Black Saddle back clowns or a nice pair of Clarkii. I change 5 g of water weekly (maybe less). My nitrate is always not detectable, and no nuisance algae. I feed my fish once a day, and expect my nitrate to continue to be 0 even when I add the two clowns.