I agree. A couple of months ago, we ended up having to move all of our tanks around in order to fit more tanks in the house. On the smaller tank (a 75), we saved the water, because the water heater had run out of hot water, and we needed to transfer the fish immediately. However, on the 180 and 125, we added all new water. All three tanks are fine. If your filter is going to off for a while, it's a good idea to move media into a shallow pan with tank water so that oxygenation can still take place. There's no need to save the water -- put that energy into ensuring the bacteria in your filters doesn't die.