I recently bought some 40" Atacama Nexus stands for my surrounds and have been researching mass loading. My stands have a center column that can be mass loaded and is approx. 2" (diameter) by 39". The center column has about a fingers width of space to pour a substance into the column. After my initial research I came up with aquarium gravel, BB's and sand (play box) as possabilities. Since I rent the stands need to be moveable at a later date. I looked at gravel at WallMart and realised that I'll need quite a bit. Do I want the smaller kind so it packs tight or the larger so I need less volume? It occured to me that gravel being hard may rattle. But once it's all in the stand perhaps it's negligable? Also at WallMart I looked at BB's. I hadn't realised how heavy they were. I figure 1 box would fill 8-10 inches and be heavy. Not sure if I want to do the whole volume though. Perhaps 1 box of BB's on the bottom to add weight and then another substance to take up the volume? I didn't really want to mess with sand but it certainly makes sense after seeing the gravel and BB's. What I'm unsure on is if any sand could leak from the stand? And if the sand would come out easily when I came to move? I'll guess that if it stays dry it should fall or push out. Any thoughts?