tha sand is probly 2yrs old its not dirty tha tank has been sittin for a few months with only bout 8 inches of water above it its a hunded gallon tha power heads have still been on tha hole time water doesnt smell at all n has been very cold salinity is thro tha roof bout to start up tha tank again n im maybe thinking bout freshning up tha sand*** some one on my other post sugested it