You can reuse it. Just make sure it gets rinsed really well. Take a garden hose and start rinsing in the pail. Put the hose in the sand and turn on the water just enough to get the water to move the sand some and for the water and just to overflow the pail and all of the gunk with it. Do this until the water runs clear. (gonna have to ensure you are moving the hose around some in the pail to get all of the sand moving and th gunk out)
Since it is getting nice out now I would get a tapr and lay the sand out to dry after it is clean.
JMO let's see what others say.
Oh yeah, post some before and after pictures of the tank and the sand if you can. Will help others along the way to see them.