The MARINA Floating Thermometer
with suction cup is accurate and easy
to read. It has a safety zone indicator
for most tropical fish. Protect your fish
from unsafe temperatures. Simply
suction thermometer in the aquarium
and you are ready to go. For fresh or
I bought two, and as a test placed them both into the same tank next to each other: one reads 78 F, the other 82 F. They are clearly not very well calibrated, but this is endemic to alcohol-based thermometers and I was expecting this, so I will personally calibrate and mark them as being off by X degrees for accurate use like I do with all my alcohol-based thermometers.