How to stop powerhead noises?
 

I have a Tunze nanostream that has decided to start rattling and vibrating. I cleaned it up and adjusted it once and it stopped for a while. Then it started again. Is there a way to rid this problem without having to track down a new impellar? It reminded me of when my fluval would start being noisy and I had to replace the inpellar. Is there a lubricant that is reef safe that would guiet down this noise?