they are called mesentary (sp??) filaments. this is a common reaction to stress is in general and is not good but they usualy recover if the stresser is removed. the fact that it has done it a couple times is not good - something is wrong. mine will do this only when i frag them (an obvious stresser). you will need to discover what the issue is or you may lose it. the above suggestions and recomendations are all good...... move it down and leave it be, best to disturb it as little as possible till it acclimates to your tank.