If you want to, you can get rid of the floaty stuff by leaving it sit in a bucket overnight, and scooping out the bits and chunks that remain floating the next morning. You might have to do this a couple of times, as Aquabruce said, and you will lose a lot of soil, for sure - but nothing but the softest mud left behind. You could also go the extra mile-and-a-half and mineralize it - but that's a whole 'nother thing. . . lol.
You should be fine with just tossing it in, capping it with sand, and carefully filling the tank, as the others said, but if you really wanted to get rid of the floaters - it can be done with a bit of extra patience!
Good luck! Dirt is so lovely in a tank! ^__^
Last edited by Chesh; 12-15-2013 at 12:30 AM..