Hi folks,

We all talk about how cold we keep our planted tanks or shrimp tanks. But have you ever wondered if your 24 degrees is the same as mine?
Have you ever calibrated any of your thermometers, temperature controllers or chillers?


I recently compared 2 temperature controllers, 2 chillers (Arctica and Hailea) and 2 cheapo alcohol thermometers.

They are ALL reading differently.

The following method is only going to be useful for digital thermometers but if you can be bothered to put "offset" stickers on your non-adjustable thermometers, then this will also work.

First, get some crushed ice.

They must be crushed. If you cannot get any, simply wrap some ice cubes in a towel and smash it against the corner of your tank...I mean wall, WALL!

Once you have the crush ice, put them into a container and add tap water slowly. As the water melts the ice, the ice level will drop. Stop adding water once the water covers 3/4 of the ice. This is to prevent airspaces between the ice.

Next, stick your temperature probe into the middle of the ice.

Make sure it does not touch the wall of the container.

Then wait for the reading to stabilize. 10mins should be more than enough, and make sure the ice are all still there, don't wait till there's only water left.

Well well...my sensor is 0.3 degrees off.


If there is a way to do the offset for your thermometer, then simply reset to zero.


For those simple digital thermometers or alcohol ones, the only way is to write down the difference and stick it on the thing so you'll know how much to add or subtract from the reading in the future.

Now, how to calibrate a chiller then? I would not suggest pouring crushed ice into the chiller, especially if it is already in use.

Unfortunately, the only way is to first use ice to calibrate a digital thermometer and then using that thermometer to check against the chiller's reading and doing the offset (if the chiller allows this. If not, simply write down the readings and set the chiller's kick in accordingly).

One last thing. Remember to only check the chiller DURING THE TIME IT IS NOT RUNNING. A running chiller's sensor may sense the chilled water coming out of the cooling chamber and will not always be accurate or same as the tank's temperature that the calibrated digital thermometer is sensing.

So the next time we talk about how well our shrimps are doing at 24 degrees, they should really be in 24 degrees. Not 23 for me and 25 for you!