<a href=showthread.php?s=&postid=11647993#post11647993 target=_blank>Originally posted</a> by SaltyDr
I would guess that there is a fair amount of nutrient build up in your sand. I'd save a few cups and then wash the heck out of the rest if you plan on re-using it. If you don't wash it you run the risk of high nitrates and phosphates in the new system. Since you aren't talking about a lot of sand, I'd save a few cups to seed new sand and not worry about the issue (plus the effort of cleaning the sand).