Foam Bottom

[Lauralai]

I have a question with the foam base. Does it have to be the blue or pink foam or is that they better option?
I went to the local building supply store and they said that you can use the white plastispan normal Styrofoam stuff. I'm trying to get the most economical pool base, possible and the platispan can be bought at home depot for 12 dollars for 1"x4'x8' sheets that have plastic on both side to help keep it from breaking
.
My pool install directions say you can use Styrofoam but don't say exactly what kind.
http://www.pioneerfamilypools.ca/man...ance-Round.pdf

Their is no way I can get large quantities of sand in my back yard either, if I use sand only it will need to be carried in by the bag which could get expensive and tiring. We also seem to have a fair bit of small gravel rocks in out back yard that the more we level the more we find that I don't think I can get out. Has anyone tried sand and the laminated floor under pad foam stuff to help the bottom be smooth??

The pool is an AG 15' round and we started the leveling process today. It will probably be a few more days before we get it level.
Thanks