From what I have read, you wouldn't really be able to sustain them due the fact that they get their food from the water column. While corals feed this way, barnacles get much larger and require more food. My guess that if didn't die from temperature (As pointed out above) it would eventually starve (and probably foul your tank from all the feedings in the process). Another issue is that they reproduce en masse. Once they affix themselves to something, they do not come off...easily, and they reproduce in large numbers as a protection mechanism. From what I read, I think this would not be a very tank friendly addition.
To fail to plan is to plan to fail.