if you want to go really green, setup a couple rain barrells, plumb them to some barrells in your house, use that water to refill the tanks (no need to remove chlorine but you still would probably want to filter) again where I live the rain water is pretty clean, may not be so much elsewhere (also having barrells inside the house give the water time to get to room temp at least)
and I think using the same mechanism th toilet uses for the sump would be best, or make it really easy and use a toilet bowl for your sump
hmmm, got me thinking, this might work well on my 700 gallon (planning all kinds of DIY filtration, but that is another thread for another day)