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.
