Re-using / washing sand bed

[Default]

I did have a nitrate spike out of the blue at about 9 months. It went to 15ppm in a week and took six 50% water changes to get back down to 0.2.
It could have been caused by the sand now that I think about it.
I think most of the bad stuff is in the sediment that is rinsed out. If I did it again I would buy new sand the smell is awful I was gagging while scooping and rinsing.