I usually mix up 5 gal of saltwater at a time.My RO/DI is in the garage and i didn't realise how cold it was out there.I figure the bucket was about 70 when i added it to tank.Never measured temp at all.Thing look pretty good today,I figure in nature,there are cold upwelling currents that hit the reefs periodically so they probably tolerate it well.If it had been too warm,now then i probably would have had bleaching/RTN