First, thanks to all who respond ahead of time. I've been an aquarist for a long time and I'm familiar with cycling etc so no need to get deep into the basics. My issue is this. I am finishing my basement/fishroom and doing so will have to move my tanks. Right now I have two I need to move but they are currently stocked. In order to move them I am going to need to empty most of the water and remove the fish. Not only that but I figure since I'm doing it Im going to do a complete overhaul. Im changing out my gravel substrate and going with the black diamond blasting media that I've been hearing tons about. So I will have all new substrate. Also in the new location I will have to completely change filters on both the tanks. WHat is the best way to go about doing all these major changes and then replacing the fish without killing them? All suggestions welcome. By the way, I'm going from HOB filters to canisters so they can be hidden under cabinets. THe tanks are being built into a two way veiwing wall. The fish are both large cichlids. Thanks again!