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Digital aquarium thermometers, strip thermometers, accuracy


Temperature inside your aquarium is something that needs to checked on a daily basis. It is crucial to your fish’s health that they are kept in an environment that is best suited for them.

Most fish and invertebrates are cold blooded, they can only maintain their body heat from the environment that they are living in; incorrect temperatures can affect their metabolism in all sorts of ways. Large changes in the temperature are not a good thing in any aquarium. When I perform water changes in my tanks I always preheat the water that is going in, not all keepers do this, so checking the temperature for sudden drops as they refill the tank is vital. Make sure the water is added back slowly, giving it time to reheat this is the only way around this problem.

Incorrect temperatures can cause the following problems:-

  • Illness caused by stress
  • Death brought on by stress
  • Reduction in the appetite of the fish, this in turn will reduce the capability of their immune system.

Every aquarium must have a thermometer fitted, most fish require a temperature of 75°F - 80°F (24°C - 27°C), however some species will require higher or lower temperatures to live happily, always research the fish before you buy.

Most of the original thermometers were alcohol, glass ones. Simply they worked by the alcohol expanding with heat and rising up the tube from a storage bulb at the bottom, a simple gauge at the front of the thermometer is all that is required for a reading. These were attached to the aquarium by means of a sucker arrangement.

Digital strip thermometers were the next step; they were attached by actually sticking them to the front of the aquarium on the outside by means of a sticky backing. As the temperature increased the scale on the strip would illuminate with assorted colours, depending on the make, a reading is then available from a further distance as the strips stand out more than the internal glass thermometers.

Disadvantages of using the glass thermometers are that you need to be right in front of the aquarium to get a reading; the digital strip allows you to get a reading from further away. The glass thermometers, after a period of time tend to get a coating of algae, because of this they need to be removed for cleaning.

Disadvantage of the digital strip thermometers - how accurate are they?

The temperature is measured from outside of the tank, this means that the heat has to travel through the glass before a reading can be taken, also they can absorb some heat from external surroundings.

Nowadays there is a new range of digital thermometer available. Most of these are battery operated with a clear crystal display; this means that reading the temperatures is as easy as a quick glance at the aquarium.

Many are fitted with a probe that sits in the water; this can give an accuracy of plus or minus of 0.5 of a degree, these can be relied on much more in my opinion.

I currently run two thermometers one at each end of my tank, (temperatures can vary if the water flow is not correct.), they are mounted on the outside of the tank by means of a velcro arrangement, the probes are then placed in the water, suckers securing them.

The display can be either Fahrenheit or Centigrade, whichever is preferred. Battery life in them is well over one year or 5000 hours constant use. I can literally walk into the room containing the aquarium and with a quick glance make a note of the water temperature, much better than peering into the tank glass trying to get a reading.

There are some models that are completely submersible, these sit inside the tank also and are mounted by means of a sucker arrangement. The advantage to these is that there are no wires hanging from the thermometer for the fish or plants to get tangled in, everything is self contained, this is much better for the aesthetics of the tank. Another advantage of this type of thermometer is that it will display the temperature down to one tenth of a degree, how accurate is that reading.

Yet another design adaptation to this type of thermometer is the floating design. It literally floats on the water surface giving readings all of the time, usually a clip is attached incase the fish keeper wants to secure it on the side of the tank. As it is a floating design other uses for it are in swimming pools and hot spas so these are very versatile. If it is accidentally dropped in the tank, no problem, it will simply float to the water surface again.

The prices for the glass and digital strip thermometers are definitely at the cheaper end of the market, normally you would expect to pay no more than 2 pounds (4 dollars) for these items, but for piece of mind paying out slightly more for a more accurate model makes sense to me.

We are not talking a lot of money here, a basic digital thermometer with display screen and wired probe costs as little as 5 pounds (10 dollars) up to 10 pounds (20 dollars) depending on which model you decide to purchase.

There are a lot of these coming over from Hong Kong at the moment, very reasonably priced, with as much reliability as the well known makes, just check the postage before ordering.

For slightly more money, these can be purchased with added features.

  • Large display – this is very useful for people with poor sight quality, or if viewing from a larger distance.
  • Aquarium temperature display plus room temp display – sometimes the room temperature can have a detrimental effect on the tank temperatures if too high. In this case a cooling fan would help out.
  • A built in alarm for out of range temperatures – the temperatures can be set so that if they drop below a certain level or above a certain level an audible alarm will ring out, warning the fish keeper.

To benefit from these extra features it will still only cost you anywhere from 15 pounds (30 dollars) up to 25 pounds (50 dollars), depending on the model you choose.

Accurate measurement of aquarium temperatures is a must, not just done for fun; your fish depend on them being right, always buy the best model you can afford.

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