Used play sand in some of the planting beds, not in my hole pond bottom though, larger river rock, pea gravel is what i use in most of the pond planting beds. The fish pretty much leave the sand alone, the koi sift through it but pretty much spit it right back into the bed, none of it really gets kicked into the water column.
Quikrete 50 lb. All-Purpose Sand is a washed coarse sand that can be used as underlayment for brick pavers and flagstones. This sand increases traction on snow and ice when applied to slippery surfaces.
Would this sand be appropriate and safe? I plan on washing it prior to putting it in as well
Is the sand for looks or to protect the bottom from tears to the liner? I just leave mine bare and let the nice short green carpet algae cover the sides and bottom. Sand might make it hard to use a net to scoop out any muck that accumulates.