mouse pad
I use a rubber Matt that is food safe and has a wide temperature range tolerance. I think it's 30A Duroneter. I use it under my return pump, my skimmer, and in my salt mixing vat. The reduction in noise is significant and it makes vibration all but undetectable.
Bulk Reef Supply sells a pad to place under it to dampen vibration.
Where did you get yours?
I always use a polyfilter... Great for absorbing vibration and great for absorbing Copper in case of an accidental heater break. Replace it every 6 months, great insurance policy for about $20 a year.