i can see the water thing a bit !! reason why i think alot have issues with water changes is that the new water will never really match your tank water exactly which could cause some shock!! the reason why i feel its best if you can to have your sump big enough to pull out 20% for your bi-weekly change and keep your pumps running !! then syphon thru a airline the new water back in !! then your change isnt noticed !! what i do and think it easier on me and the tank!!
I agree. I purposely bought my overflow box larger than I needed so I could pump my water changes into the overflow and let it "pass" through the system before it gets to the tank. It seems to work OK for me. It takes a little more time to do but it seems more "natural" this way.
125 Gal-35 Gal Wet/Dry-Tetra-Tec PF500 HOB
(3) AuquaClear 301 Powerheads-600 GPH
Automatic Tempature Controller
5-6 Inch Sand Bed-200+ lbs of LR