Most Reliable Thermometer?

What is the most accurate/reliable thermometer? I've read that mercury thermometers can be off by a few degrees, as well as digital thermometers. Any suggestions, or the type you use would be awesome!

 

I was using a Coralife digital for a while. It worked ok usually was off by a degree or two. Now I have my Aqua Controller Jr and that has a Digital probe. Seems to be almost dead on compared to the coralife digital. If you can afford it I would look at a controller .

 

I use a JBJ True Temp controller connected to a number of heaters that have their own internal controllers.

What this does is give me a fail-safe on the temp control part of the heaters. If the controller fails "on" then the internal controllers on the heaters act as a backup "off" mechanism. If the controller fails "off" the worst that happens is there is no heat and that is far less "fatal" than cooking your tank (unless you live in Green Bay). If you wanted to fail-safe that you could do it with a small second heater set to a low temp to keep your system from getting to critically low temperatures without enough power to cook the tank if it failed on.

I also have a controller and I run the temp probe. The temperature readings between the JBJ and Apex controller are identical.

The reason I use the JBJ is that I like being able to see the digital temp readout in nice, big, red numbers.

 

I was looking at the 150 for my nano. It looks like a pretty nice product. I might even get the ATO they make while im at it.

 

I had a couple corallife digitals and they were both off by many, many degrees. Absolute junk. Most digital thermometers aren't very good actually. some of the higher end ones, for controllers are better, but I trust nothing as much as the cheap $2 alcohol thermometers. The ones with the little suction cups that they sell at most fish stores. I haven't had one fail me yet...

 

Ranco temp controller. Only way to fail proof.

 

I have the ATO too. Nice, inexpensive unit with all the necessary fail-safes.

 

Yea, I was using the Coralife digital ones in my Cichlid tank for years. Until I switched to saltwater tank then I realized at setup time that something was not right with my heater temperature probe calibration, or so I thought. Then I stuck my second Coralife digital unit in and guess what? They were 5-6 degrees different! I took others advice and went back to a cheapo habg on the glass one. Much better now!

 

OK. I think I'm going to go with the $2.00 alcohol glass thermometer. It may not be all "High-tech", but it gives me an accurate reading. Thanks, everyone, for your imput!