I'm thinking about making a waterfall

[wiperhunter2]

Well, I did not get as much done on my waterfall pool as I was hoping this year but I did find a pool at a yards sell and I got it installed. Next year, I plan on building the waterfall, here are a few pics I took after I got the pool in, the pile of dirt beside the pool is where I plan on putting the waterfall. Question, the pool came with this plastic box that has round white plastic pieces in it, any idea what they are or what they are used for? I'm assuming they are some sort of filter, but with them just randomly laying in the bottom of box, I have no idea how they work.
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