I see, how about filling some small, heavy-duty plastic bags with coarse sand, these can then be sealed and added to the big sandbag (double bagging for extra protection against anything escaping, if required ) to give the right weight as needed? Don't overfill the bags though, that way they might be less likely to split if you accidentally drop them! If you're concerned about sand escaping and getting into the moving parts of the tripod/stand/camera, etc. then you could perhaps use some of that rounded ornamental stone (about the size and shape of a kidney bean) they sell at garden centres, and wash it first to remove gritty dust, before drying it and packing it in the plastic bags? Using inert building materials is probably better than using feedstuffs, as over time food could attract vermin (rodents, larder beetles, flour moths, etc.) and/or swell up if the bags get wet or damp? Hope this gives you some ideas to consider and is useful.