I've used 4 different thermometers in my tank and all are giving drastically different temps. I first used a digital one that was way off, saying the water was 81 when I didn't even have a heater in it. I now have a heater and 3 alcohol thermometers. I did the ice test on all 3 too to make sure they're accurate. The one that was the most accurate is currently reading 71. The one that was 6 degrees too high is reading 87 and the one that was 7 degrees too high is reading 86. I have no clue which one to believe, it's incredibly frustrating. I'm willing to pay some good money for a thermometer that actually works if you guys have suggestions.