OK guys, here's the deal! If you spend a little time plumbing, you can run filtered water water into the "outlet" (return) side of your sump, and have an overflow in the "intake" side of your sump that empties into your household plumbing.
You can then choose to open the supply valve wide open and watch your water temp. and turn it off when you see the temp. drop a couple of degrees, or you can let it trickle slow enough that the water is changed out without any temp. variation.
It might be a little more work initially, but only having to open a valve to do a water change-------PRICELESS!!!!