Diatom filters

After unsuccesfully dealing with persistent green water and cloudy
water issues in my tank for the last few months, I broke down and
bought a Vortex D-1 diatom filter today. Quite frankly, I am amazed
by this thing. Within 1 hour, my water turned from a hazy green, to
crystal clear. I do have questions though-- the instructions aren't
very clear, how do I store this thing once it is finished? I can't
just leave the water in it, right? The instructions mention flushing
the unit out, but won't that also flush out the filter powder along
with it? Sorry if these are dumb questions, but I've never worked
with one of these before. Thanks for any insight or useful tips.