i kept a pair of Janss' (Doryhamphus janssi) in my reef for years. flagfin pipes do well in mature reef systems.
you need to be careful with bluestripes (Doryhamphus excisus), as two males will fight to the death.
i recommend bandeds (D. dactyliophorus) or Janss'. IME, yellow-banded (D. pessuliferus) and multibandeds (D. multilineatus) are a bit more touchy and even when eating seem to fail to thrive.
folks also keep dragon-faced (Corythicthys sp.) pipes in reefs, but they're a bit harder to feed due to their small snout size. i've never kept them myself...yet...