Oh yea, sorry I missed a part you asked what I'm using to measure. I have a "All Living Things (ALT)" Thermo/Hydro prob and an additional normal temp prob that way I have three probs, one on hot one on cool and the hydro is right in the middle of the tub. I know ALT is not the best brand, but I needed one in a pinch and it seems to be accurate. I have a cheapo hydro/temp in my bearded's cage (just because it was laying around unused) and the ALT seems to be more predictable.