I have about 12 Coralife Digital Thermometers and NONE read the same temp.. some are 5 degrees off.. As of right now I use a Lab grade Floating Glass Thermometer from my beer brewing days and a Lifegard Aquatics Big Digital Temp Alert just for the Alert feature but even that is 4 degrees off from the Glass Thermometer so i just have the alarms set at a average difference.. So i was just wondering what others use and do you really trust it on how accurate it reads