It depends on how large of a water change in doing, if I'm doing 10 gallons or more I will take a spare power head and blow all the detritus from the rock work and then siphon out the water along with all of the floating particles in the water column, if in only doing 5 gallons then I will use a smaller diameter house and poke it around in the rock work and siphon out as much detritus that I can without getting it all stirred up and floating around the tank
I have a RSM130D so I will also siphon out the back compartment by the intake and skimmer, I attached 2 pieces of tubing to the intakes of the return pumps so that they pull there water from the bottom of the return chamber so that I don't get any detritus building up on the bottom because I had noticed before that I was getting alot of detritus buildup in that chamber and this was a very simple but very effective solution to stop that from occurring and causing nitrate and phosphate buildup in the tank