the PFS is a big enough grain that you shouldnt have to cover them, just have them raised a couple inches from the bottom and your golden, im sure they have it especially now that its summer time, sometimes they wont have it in the winter, but i would check it out at the store im not sure if thats comething they would post on their website but yeah its like $8 for a 50lb bag here and its not super fine the the play ground, sand box stuff, that stuff is super fine and will go into your filter you want the sand specifically for pool filters, and then just rinse it well and it barely even makes your water cloudy