Anyone ever use the sump water for their water change? Seems like it would be less disturbing to the fish and you can pump back in the exact water level you need again (bit of a guess when filling up display and then kickstarting the return pump again). I have a Waterbox 110 (79 display, 31 sump). So relatively huge sump for that size tank. Could easily grab 20-25 gal from sump. Downsides?
