How To Maintain Water Temperature In Fish Tank? (Best Ways)

Temperature is one of the most important parameters of water in an aquarium.

Incorrect temperature conditions can quickly provoke serious diseases or even kill underwater inhabitants. Absolutely all processes occurring in aquarium water directly depend on its temperature. How to maintain water temperature in fish tank is not a hard thing.

how to maintain water temperature in fish tank

Why Does Aquarium Temperature Matter?

The role of the temperature regime is difficult to overestimate, since it affects absolutely all the inhabitants of the aquarium, plants, and even biological processes in the water.

How does temperature affect fish in an aquarium?

Too low indicators undermine the immunity of the fish , and it becomes sensitive to many diseases.

Often, hypothermia leads to the so-called semolina ichthyophthiriasis.

This is a dangerous infection that spreads quickly and often leads to the death of the inhabitants of the aquarium.

In the cold, most fish feel uncomfortable, they become lethargic, refuse to eat, and lose their color.
Coldwater is the most dangerous for fry, since it does not grow in it, and in just a few days it becomes “tightened” – it will never be able to grow to its normal size again.

In too hot hydrobionts often experience oxygen starvation, since the warmer the water, the worse the gases dissolve in it. As a rule, the fish does not die from overheating, but from suffocation caused by increased temperature.

what is Effect of Temperature on Aquarium Plants?

Most types of aquarium plants come from the tropics, so they do not tolerate hypothermia. If the degrees are below 24 ° C, they slow down growth, and if below 20 ° C, they die.

Overheating causes no less sad consequences.

The higher the temperature, the faster the consumption of nutrients by plants, but at the same time, too warm a liquid cannot be saturated with carbon dioxide.

Namely, carbon dioxide is the engine of growth, so plants “eat away” available nitrates/phosphates as long as there is at least a minimum CO2 value in the water.

But this happens in just a few hours, then algae come into play, for the growth of which carbon dioxide is not so important. And instead of a beautiful underwater garden, the aquarist gets something that looks more like a swamp.

effect of temperature on beneficial bacteria in aquarium

Not only fish breathe in the aquarium, but also beneficial bacteria that process all waste into safe compounds.

Since there is not enough oxygen in a too-warm environment, some of the bacteria die, and the rate of the nitrification process slows down. The appearance of ammonia/ammonium and nitrite in the water has a toxic effect on all aquatic organisms without exception.

best temperature for fish in celsius For aquarium

For each species of fish, it is necessary to maintain a different temperature regime, this should be taken into account when choosing the tenants of the aquarium.

best temperature for fish in celsius for aquarium

best temperature for fishes in celsius chart:

Type of fishOptimum temperature, °СPermissible temperature, °С
Viviparous fish (guppies, mollies, platies, swordtails)24-2522-27
Carp-toothed (barbs, cardinals, rasboras)24-2624-26
Small characin fish (neons, tetras, hasemanias, minors)24-2623-27
African cichlids (Malawians, Julidochromis)25-2624-28
American cichlids (angelfish, cichlosomes)24-2524-26

The table shows the parameters for adult fish, for fish fry, and adolescents, the optimum temperature is always 1-2 ° C higher.

What temperature should aquarium plants be at in celsius:

With plants, the situation is the same, many of them do not tolerate warm water, many of them hypothermia:

PlantOptimum temperature, °СPermissible temperature, °С
key moss18-2014-21

 For most aquarium plants, the optimum temperature is 24-26°C.

What temperature should a saltwater fish tank be? Marine Aquarium

In a marine aquarium, as well as in a fresh one, the optimal values ​​​​are 24-26 ° C.

In warmer water, hard corals begin to experience calcium starvation, which prevents skeletal development. In a cool – development slows down significantly.

Soft corals can withstand temperatures from 23° to 29°, hard corals 24-27°C.

The greatest danger is the increased temperature for fish, because, just like in a freshwater vessel, oxygen is poorly dissolved in a warm environment, and the fish suffocate.

how to maintain water temperature in fish tank?

Sometimes the temperature regime gets out of control and requires urgent action to maintain water temperature in fish tank.

how to raise water temperature in fish tank?

There are several ways to raise the temperature in an aquarium:

  1. Changing or topping up with warm water. Just drain 20% of cold water and add warm. It is better to do this gradually so as not to cause stress to the inhabitants.
  2. Install powerful lamps . Lamps are a fairly strong source of heat, especially when it comes to incandescent lamps. By installing 3-4 of these bulbs above the surface of the water, you can increase the temperature in the aquarium by 3-4°C.
  3. Use an aquarium heater. The most reliable way that does not cause unnecessary stress to the inhabitants. The device will not only heat the water, but will also maintain the set temperature.

how to lower water temperature in fish tank?

In the summer, this problem is especially acute, but it also has several solutions:

  1. Using an aquarium air conditioner – chiller.
  2. Homemade cooling device based on a computer cooler.
  3. Ice and cold water. But you need to be careful, sudden drops are no less dangerous, especially since this way you can cool the water too much.

how to keep aquarium temperature constant?

It is important to keep the temperature constant. For this you need:

  • Use only a high-quality heater, and control its operation with a conventional alcohol thermometer.
  • When making changes or adding water to replace evaporated water, it should be heated to the temperature of the aquarium. To do this, it is best to have another heater.
  • Do not install the aquarium near heating systems or kitchen appliances that emit high temperatures (ovens, slow cookers, stoves).

how to regulate temperature in a fish tank?

In order for the inhabitants of the aquarium and plants to be comfortable, it is enough to set the temperature regime once.

All you need is to buy a heater, but its choice should be approached thoroughly:

  1. Particularly cheap Chinese models are of low quality and quickly fail. Well if such a device just turns off and the fish sit in cold water for a while, but it happens that the heater sticks and it does not turn off, turning the aquarium into an ear.
  2. It is important to pay attention to the thermostat step. Some models have a step of 2-3 °, this is unacceptable. The step should not exceed one degree.
  3. Power is the most important nuance in choosing a heater. A device with a power of 25W is simply not able to heat a 100-liter aquarium. There is a golden rule – 1 W per 1 liter. (For a 50-liter aquarium, you need a heater with a power of 50W, for a 200-liter aquarium, 200W).
  4. Suckers. This point does not affect the performance, but sometimes you can find heaters on sale with such “oak” suction cups that the device does not stick to the glass. Suction cups should be soft and easy to wrinkle in the hands.
  5. Be sure to have an LED indicator this allows you to understand whether the device is working.

Heaters Tetra, Aquael, Eheim, and Juwel have proven themselves best.

After the heater has been purchased, it must be installed. It is best to attach it to the glass where the filter (or the outlet of an external filter) is located, so that warm water is carried by the current.

The device must be completely submerged under water, but some models allow you to leave the regulator on the surface. No matter how high-quality the aquarium heater is, its operation should definitely be monitored using an ordinary alcohol thermometer.

It is better to place the thermometer as far as possible from the device, then its readings will be the most accurate.

When keeping demanding fish that require a certain temperature, it is worth putting 2 heaters.

If one device fails, the other will continue to work. This is true for marine aquariums, discus, demanding types of expensive cichlids.

How to Measure Aquarium Temperature?

There are several ways to determine the temperature of aquarium water: using a thermometer, an indicator strip, and focusing on a water heater.

how to measure aquarium temperature

Measure Aquarium Temperature with Thermometer

There are several types of thermometers used in the aquarium trade, and each of them has its own advantages and disadvantages:

  • Alcoholic. The most accurate, but since it is made of glass, it is easy to break.
  • Electronic (internal). Also quite accurate, but expensive.
  • Electronic (remote). Only the sensor is placed in the water, the digital display remains outside the aquarium. Differs in a high share of an error.

Alcohol thermometers are the most popular, as this is the best price/quality ratio.

Measure Aquarium Temperature with Heater without using Thermometer

Modern aquarium heaters are equipped with a sensor. When the device is working – the light is on, when it heats the water to the set temperature – it will turn off and the light will go out.

You should not seriously consider this method, since the heater may fail at any time, it may jam, it may not work quite correctly.

Measure Aquarium Temperature with test strip

This is a crystal thermometer that is glued to the aquarium glass.

Depending on the temperature, a certain area begins to color on the strip, the inscription on which corresponds to the temperature of the reservoir.

Such a strip looks quite aesthetically pleasing, but the accuracy of its readings leaves much to be desired.


Only by maintaining the optimal temperature in fish tank or aquarium, you can achieve the natural and bright color of the inhabitants and the healthy growth of underwater flora.

Buying a heater will cost much less than treating fish or finding new plants. Therefore, it is worth purchasing this device even before the inhabitants move into a new house.

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