Ok here comes a face-palmer. I just added an area of sand to my gravel substrate while fish were in the tank, about 50% of water removed. At one point during this process I noticed the sand was cooler than room temp and was making the water cold. So I then overcorrected adding warm water and my tank went up about 5 degrees from normal, so currently 80 degrees. I was going to then small amount of cooler water, but sometimes in the heat of the fish moments as I already showed once so far, we don't make the brightest decisions. So should I let the temp come down naturally and hope nobody dies or add some cool water (and hope nobody dies)?