Gina and I had a pair for quite some time, perhaps a year or so. They did eventually die, I suspect it was a matter of stiff competition for available food. In my experience, they don't take mysis (to big I think), but feed well on cyclops and other small foods. They also graze the rockwork constantly and can be observed picking small stuff from the cracks and crevices. I cut down feeding the small stuff too much as a means of nutrient control, but I fear this may have contributed to their demise. In a tank as large as ours, with such high flow, a good deal of food must be introduced for it to be taken up, in a smaller system, this could likely be more easily controlled, and the pipefish more easily target fed.
If you have many pod hunters in your tank, I would recommend regular supplemental feeding with smaller foods like cyclops and such. Both of ours readily ate this type of stuff immediately upon introduction.
They don't seem to mind high flow, and are quite capable of navigating about a high flow reef tank. They also seemed to be pretty indifferent to the presence of other fish within the tank and movement outside of it. They are however somewhat reclusive, and seem to prefer spending most of their time in shaded areas such as overhangs and caves. When they move about the tank, they tend to stay low in the water column, and close to the rockwork for the most part, but again, when they do come out "for a stroll" they seem to utterly ignore their tankmates and don't seem to be easily spooked. I suspect their tendency to hang out amongst the rocks and corals is more a function of where there food is at than them being afraid, though I am sure that protection from predation must play into it to some extent...
That's about all I can think about at the moment, hope it is helpful.