I just bought 2 of these and are using both in a single ten gallon to assure accuracy. Initially I was worried because there were variations in the thermometer appearances and temperature in the store... But to my surprise I got these home and they read the same on opposite side to my heater. No they do not "sink" to the bottom. They stand like the website's name suggests. I actually prefer this as I don't have to go fishing to the bottom for my thermometer. If you want this to stay in one place I would suggest taking a spare airline suction cup and tying it in place with some twine or equivalent. I only knock one star because this is not a long term review. Ps. these can be difficult to read if you do not remove them as they spin around without being anchored.

Does not sink, floats upright, it is accurate but it doesn’t do what it’s supposed to do SINK.

While it doesn’t sink., it can be partially buried in substrate to keep it down. Despite these issues, it’s accurate and does the job.

Great glass thermometer, but has 1 issue. I performed the ice water test and it’s 1-2 degrees within 0 so it’s fairly accurate. The rubber that protects the bottom of the thermometer prevents it giving a more accurate reading. I recommend pulling the protecting cap slightly down to expose some of the metal beads to the water. This thermometer is more accurate than the suction cup ones.

This thermometer does not sink! (character limit ))

As soon as I took this out of the package and set it on the counter it shattered. Don’t buy is.

This thermometer is called SINKING THERMOMETER. only problem is that it doesn’t sink. I feel like I got ripped off for some reason. I’ll be returning this item. If you want a thermometer that sinks - don’t buy this

I wanted a sinking thermometer. This floats on top. I just adjusted the digital unit to read bottom, so it works.