Do I need to use filler in my speaker stands?

I would fill them if the stands you have allow it. Not only will it increase weight and stability, it will reduce resonance.

Here is another alternative to sand. I use crushed industrial quartz in my 24" monitor stands. Cost about $3.00 for a 40 lbs bag at your local Honme Depot, Lowes, etc. Its cheap and heavy but does give off dust while pouring. Just use a funnel while you are filling your pillars and when full, simply wipe away the dust that settles on the stand. So its best to do it outside or in a garage. I have a pair of B&W STAV24 stands and I filled each pillar to the top and each stand took about 20 lbs of fill. So a single 40 lbs bag was ideal. They are very, very stable.

Thanks Paraneer! That's a new one to me.

I just got the b&w sta v24 stands today and filled them all the way to the top with a bag of "play sand" from home depot. No leakage and not too messy or time consuming to fill them (in the driveway of course). it took me less than half an hour to assemble and fill the stands. I have them sitting flat on inch thick granite on carpet. It's easy to move the stands (with the speakers on them) this way, makes the stands more stable and looks good to. My speakers sound great set up this way and even when cranked to the max, there is zero vibration coming from anywhere on the stands. I'm in the camp where I don't really want anything in my room resonating except for my speakers themselves (speaker boxes not included) That's why I've reinforced the doors and the one window in my listening room. By the way, I think these b&w stands are absolutly great. I'll be buying another pair to use side by side for my center channel which should create a nice clean look, matching my front right and left stands :-)