[fiveldsp]

I guess I always figured that just the process of changing the water itself added enough stress to the fish, so i do what I can to make the water going into the tank as close as possible to the water coming out. I have heard people say that when they do water changes, the water they put in the tank is 3-5 degrees cooler, which would cause it to sink to the bottom of the tank so they could continue siphoning off the top. I dont know if it works like that, but it's something I've heard over the years. Good luck