I am doing 10% water change in the morning, then another 10% in the evening after the RES have been fed. This flushes out the poop and any uneaten food on the bottom of my large tank which has 255 gallons of water in it. Each water change only drops the temp 1 degree and it works very well cleaning out the tank which is why I do it. My tank temp always rebounds by the next time I feed. I do have a tendency to overfeed but like to keep the tank very clean. Keep in mind that this in an insulated aquaculture tank that keeps water temps very stable but it also makes it very hard for warm outside air temps to actually warm the water up. I have 55-60 very chunky RES in the 2-4" range in this tank.
Hey whatever works for you but it seems like a lot of unnecessary work and time to me. In the future if you add a center drain, external standpipe and a gate valve you could flush out all the crud with one pull of a handle. Better yet if it's circular tank you can inflow the water tangentially to the tank wall and create a circular flow to send the crude to the center drain which with one pull of the gate valve handle it's gone.
