the water ran from 8 last night until 7 this morning, so it was ice cold. Also in the process of all this I had a dead fish clog each of my over flows, so now I have an overflowing sump and 1000gph getting pumped back into the tank and since they were clogged now its 1000gph all over the floor. So yea, im not for sure how they all died, Just know everything was cool when I walked away from the tank last night, and EVERYTHING was dead this morning.