Well if we're talking about harlequin ghost pipefish (Solenostomus paradoxus) you would want a lower flow tank, these arent the greatest swimmers, even compared to other pipefish. To make them feel most comfortable you want to supply them with a host organism, or not so much a host but somewhere where they can be camoflauged. Every harlequin in the wild is seen next to another animal which they resemble in color. These host can range from Feather Stars to gorgonians, but I think just placing these guys in a tank with live rock and corals or caulerpa would be a bit foreign to them.
I say getting them to feed is hardest because in the beginning its likely they would only accept live foods such as benthic amphipods and copepods. The question is what species of these micro-invertabrates do they feed on. Eventually if you can get them to feed on live foods you could try transitioning to frozen mysis and cyclopeeze. These two foods are full of protien and are most commonly accepted by my pipefish (bluestripes, bandeds, and dragonface) as a first food transitioning from live. So nutrition isnt as big of a problem as is just getting them to eat in the first place. Although once eating frozen their still should be a sufficeint pod population in the tank to supplement their diet. Ive noticed in my bluestripes a huge reduction in egg count when the pod population is low.
This species hails from the tropical coral reefs of the indo-pacific so temperature wouldnt be to big of a deal, probably normal tank temperatures between 77-80.
Good luck if you find one but man are they hard to find.
