i just mess with them. i go all the way up, wack them with the crowbar, control my fall onto another barnacle tounge and repeat process.
of course there ahs to be more than one of them..
neat trick with barnicles.... in blueshift. i forget which level but theres a broken bridge with some pipes under them, thers a barnicle on the other side of the bridge, if you let it suck you up and kill it, you fall onto the other bridge and there are 2 medkits there.