The water temperature of your aquarium is crucial for the wellbeing of your fish. Water that is either too cold or too warm may harm – or even kill – your fish. That is why it is important to carefully monitor and control your fish tank temperature.
For that, a thermometer is essential. However, sometimes you may find yourself without a thermometer – that is why you are here right?
Maybe you have just set up your aquarium and forgot to include a thermometer in your checklist of things to buy, or you may have misplaced the one you already have.
Not to worry. I will teach you how to check fish tank temperature without thermometer. There are certain methods you can use, but be warned that they are not as precise as using a thermometer. They are intended as a quick test to gauge the temperature of your fish tank when no other options are available.
We’ll also look at what should be the temperature of an aquarium and the relationship between aquarium temperature vs room temperature.
Let’s get started!
What Should Be The Temperature Of An Aquarium
The ideal temperature of an aquarium should be between 75° to 80° F (24° to 27°C). Water temperatures between 70° to 90° F may be acceptable.
However, this is just a general rule – you should consider the specific needs of the fish you have to determine the optimal temperature. For example, tropical fish cannot tolerate temperatures below 60° F (16° C) or above 95° F (35 °C).
Just because your fish can tolerate a certain temperature range you shouldn’t subject them to the extremes – it is best to keep it within the ideal range.
Water that is too warm will hold less dissolved oxygen, which could cause your fish to struggle to breathe if there isn’t sufficient oxygen available in the tank. Higher temperatures may also promote the growth of bacteria and fungi, which is not something you would want.
On the other hand, water that is too cold will slow down the metabolism of your fish and make them sluggish. Tropical fish will be especially stressed when the aquarium temperature falls.
Certain fish, such as bettas, prefer warm water, while others such as axolotl like a colder environment.
Ideal Betta Fish Tank Temperature
These Siamese fighting fish are a popular breed because of their vibrant colors and elegant flowing fins. Since they are tropical fish, the temperature for a betta fish tank should be between 74° F – 82° F.
Can cold water kill a betta fish? If it gets lower than 60° F, yes indeed – if not immediately, eventually.
When the temperature gets too low, their metabolism will slow down and their immunity will take a hit. It will shorten the lifespan of bettas, as many aquarium owners have reported. So it is vital that you carefully control betta fish tank water temperature.
Ideal Axolotl Temperature
Axolotl are sensitive creatures that prefer the cold and darkness. The temperature of an axolotl fish tank should not exceed 72° F and should not go below 50° F. The ideal axolotl temperature is between 60-64° F (16-18° C).
Since that figure is colder than room temperature, you may have to use an aquarium chiller with your axolotl.
Other breeds such as goldfish and koi can do well in a wider range of 59-75 ° F.
Aquarium Temperature vs Room Temperature
Here’s an interesting question: is the aquarium temperature the same as the room temperature?
First off, room temperature is not a number that is set in stone; it usually refers to a temperature of 68-72° F (20-22°C).
Answering the earlier question, the aquarium temperature tends to match the room temperature, provided that you do not use a fish tank heater or chiller.
Even without a heater or chiller, there are other sources of heat in your aquarium, such as the filter, air pump, and other components. Your fish too produces some heat, and so does the decomposition of organic waste.
On top of all that, evaporation of water from your tank will slightly reduce your aquarium temperature relative to ambient temperature.
So all in all, your aquarium temperature will be about 1-2 degrees off your room temperature. We can use this fact to our advantage when we explore how to check aquarium temperature without thermometer.
How to Check Fish Tank Temperature Without Thermometer
You can use the following methods to check fish tank temperature without a thermometer. Remember, they are rough measurements only.
The Hand/Elbow Test
When there is no other tool, you have to resort to trusting your own hands. Place your hand in the water. Or you can use the tip of your elbow as it is more sensitive. The temperature of a human body is 98.6° F (37° C), so if the water feels warm then it is close to that figure.
Since we recommended 75° to 80° F for your aquarium, the water should feel slightly cold to the touch at these ranges. If it is too cold, your fish would be feeling it too, and if it is unbearably cold, you should heat your fish tank immediately.
Watch Your Fish’s Behavior
An expert aquarium keeper can assess the conditions of the tank and the needs of its inhabitants by observing the behavior of the fish.
When it is warm, fish tend to be overly active, sometimes even behaving aggressively. They will also change to bright colors. Sometimes, fish staying close to the surface and gasping for air is a sign the water is too warm, since warm water will have a low amount of oxygen.
On the other hand, water that is too cold for your fish will make them sluggish, so if you notice your fish being less active than usual, your aquarium may need some heat.
Check House Thermostat
When we compared aquarium temperature vs room temperature, we found that it tends to be about a few degrees off, given that there is no fish tank heater or chiller.
This means the room temperature is a good estimate of the aquarium temperature. Therefore, you can check your house thermostat to gauge the temperature. Look at the one closest to your fish tank to get an accurate reading, preferably in the same room.
Make sure you read the actual ambient temperature, not the set temperature. Thermostats have an in-built thermometer, so they should display this number.
Alternatively, if you have a smartphone or watch that has a thermometer, you can place it close to the tank to get a reading (just don’t drop it into the water).
Check Your Fish Tank Heater Display
If you have an aquarium heater, you can check the display for a temperature reading. Again, make sure it is the actual temperature and not the set temperature.
Usually, the thermometer will be close to the heating element. This is not ideal because the temperature will be higher than the temperature of the surrounding water, so you will be left guessing the actual temperature of your aquarium.
Check the Local Weather Report
If all else fails, it’s time to tune into your local weather report. This is the least accurate method of all since the sensor is very far off your aquarium and house.
You can check your smartphone for a weather report; it is usually displayed on the home screen.
Conclusion
As you have seen, you can check water temperature in fish tank without thermometer, although it is not a precise reading.
That being said, no self-respecting aquarium owner would be caught dead without an aquarium thermometer – they are cheap and easy to buy.
This time, I have come to the rescue; next time, make sure you have a reliable thermometer for an accurate reading so that you can provide the best water temperature for your fish to be healthy and flourish.
Thanks for reading!
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