This conjures in my mind that scene in 'Gladiator' where Oliver Reed grabs the slave trader by the family jewels and growls 'you...sold...me....queer...giraffes....'
As Lyn Truss would eloquently explain, it depends on whether you were sold a 'aiptasia-eating filefish' or an 'aiptasia eating filefish'.
The former is a filefish that enjoys aiptasias as part of its diet, however the latter is an aiptasia that has been caught red-handed nibbling at a filefish.
A more common example is the example of a sheep-worrying dog. Missing the important hyphen turns it into a massive woolly creature, capable of antagonising most domestic canines.
Thanks guys, just wondered if there was any comeback on live animals not "doing the job" they were sold for.
@ Buildersmate, Surely the way you describe it using an apostrophe would mean i've bought an aiptasia that eats filefish or, as your other example says, a sheep that worries dogs ?