no no no, before you add it. for sand i will pour some in a bucket or larger container (a few pounds at a time) fill the rest with water, swish it around for a couple minutes, pour out the water, and do over and over till it looks pretty clear. takes a little time, but pouring it directly in your tank will not only cloud it up pretty badly for a while, but it can be full of harmful/dirty partcles and such as well
I highly recomend using Pool Filter Sand as opposed to Play Sand... PFS has consistently sized large grains where PS is a huge variety of sizes and you will have to wash out the smaller particles. I pay $8 for 50 lbs of PFS as opposed to $5 for 50 lb of PS and I save myself one heck of a headache.
Since you found this website I'm sure you can find a Pool Store in town
...and I use PFS in several tanks with JDs in them and it works great...