Is BDS really that light? I was surprised how heavy it was when I used it. I have never used other sand or PFS to compare against it though. What do you tthink is the heaviest sand out there?
Now that your tank is filled you only have two options: 1) empty and re-wash 2) turn the filters on. If you have strong mechanical filtration, I would turn the filters on and let them to the clean up. I would make sure to stir up the BDS to get as much gunk out of it.
Compared to other sand I personally found it to be light. I didn't really notice until I started to clean it with the siphon. It was really easy to suck up.