CatladyDane

I have 3 tanks, a 10g, a 20g, & a 40g. I had the Coralife digital thermometers on all, until today. 10g became unoccupied and I decided to move the single resident of the 20g into that so I could try 2 angels in the 20g (tall). Noticing differences that seemed not to make sense (e.g. warmest water to the touch doesn't show warmest reading on thermometer) I did my own experiment. I put all three thermometers in the same area of the same tank. Result: 3 different readings, each 2 or 3 degrees different from the next. I now trust no thermometer; I'll trust my own sense of touch and my fishes' behavior. Is there a reliable thermometer out there, and if so, how can you verify its accuracy? Needless to say, I don't know which of my 3 readings was most nearly correct and I don't want to chill or poach my fish by relying on numbers. (I hate numbers anyway; too much emphasis on "count & measure" in the modern world without truly considering whether the numbers mean anything of value appropriate to the situation.) Thank you for your thoughts.

TedsTank

The thermometers we use are mass produced and can vary by 2 or 3 degrees. That variation is fine for your fish. I recently bought 4 thermometers and only 2 were an exact match of the other 2 one was a bit high and the other a bit low....not to worry... you are in the area of temp your fish require. In the wild I think there are way more temp fluctuations than we are aware of.
Have fun with your fish and worry about a couple of degrees here and there!!

aquarist48

Good morning. Remember heat rises. So if your thermometer is at the top of the tank it's going to read warmer than if it were in the bottom. I keep my thermometers in the bottom of my aquarium and also one in the tide pool of my wet/dry filter.