My new Octagon 20 Advance (no pump) finally arrived, and I'm impressed with what appears to be its easy digital control. After stablization, it held a constant 99.6 from the factory. I lowered it to 99.5, and it continued to hold well. After adding my 21 guinea eggs, I decided to put in the two inexpensive digital thermometers I have just so I'd know how far off they are from what I assume is the accurate Brinsea reading. It would be handy to know that discrepancy for future use in other situations. Anyway, both of those units read exactly the same, and they each read 4 degrees lower than the Brinsea at 99.5. This both surprised me and concerns me. Do I believe two identical-reading units, even though they are cheap ones, or the "better" Brinsea temperature reading, even though it doesn't agree with any other thermometer I have? Those 21 guinea eggs are depending on accuracy, to be sure. Any input from other Brinsea users would be gratefully received!