Wow! The weather this year is bringing out all sorts of fairly rare events. It sounds like you had 'sand algae' -- under certain conditions, slime layers with algae and bacteria can deposit calcium carbonate particles that look sort of like sand particles glued to your pool. I'm gonna post these pics for the 2nd time today; usually I post them about twice in an entire season!
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Rather than reposting everything, I'm going to ask you to read this post: http://www.poolforum.com/pf2/showthr...2469#post92469

But, please respond here, rather than in that thread. It gets REALLY messy if we try to help two people with different pools in the same thread!

By the way, like Mom said, do NOT let them put ANYTHING else in the pool, especially anything that will increase calcium or alkalinity!!