I believe the fish you're asking about is a yellow-striped clingfish, which almost always starves in captivity.
It may be possible to keep them with an urchin to feed on, but it will probably kill the urchin eventually. I've heard of people keeping several urchins to spread out the suffering/impacts on the urchin. The urchin will stunt (which some people find beneficial), but will live longer.
I feel pretty sure that the clingfish Tim is talking about is a different animal altogether. They're sort of ugly, and remind me of a short squat fw pleco.