I didn't soak mine. I didn't know I was supposed to. At first the pellets had a tendency to want to float. Not anymore though. The pellets did their soaking in the reactor.
Yes by soaking / rinsing them you get the crap off of them from manufacturing and soaking them will help them sink in the reactor so they do not float.I thi nk Daniel said something about soaking/rinsing them also helps prevent the water clouding that some people experience. I'm sure he'll chime in here on this eventually.
Sinking them will not let them clump up at the top of the reactor. If they get clump at the top of your reactor then you will not get the full effect of the pellets. Also they will not tumble.