So yesterday I went digital in all of my tanks. I picked up 7 of these coralife digital thermometers from petsmart. I get em home and I test them against the other one I had already running. Old one said my geryi tank was 79.3 (which is around where i was wanting) new coralife reads geryi tank at 81.5 . Not horrible but these all claim to have a tolerance withing .1 degree. Anyways, old one reads one of my irrtans tank @ 81, new coralife reads it at 84.2 . Way way to f*cking hot imo. So whats the deal here. How the hell do I tell which one is correct??? My old one usually read out the temp that i set the heaters to. I had the heaters set to @ 81 in my irritans tank and it read 81.