What Temperature Should A Freshwater Tropical Fish Tank Be

What Temperature Should A Freshwater Tropical Fish Tank Be

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What is the ideal temperature for a freshwater fish tank?

A rather hard question to answer, without any knowledge on the fish you are keeping if you ask me.

Even so, most species kept in home aquariums are either native to the tropics or temperate regions of the world. Tropical fish make the majority of them though.

Aganist this background, the best temperature range for an average freshwater fish tank is anywhere from 72°F to 80°F. But some species like goldfish and danios will survive in temperatures as low as 62°F, while another handful of tropical species like discus and cichlids can live in temperatures as high as 82°F, or even 84°F.

That said, most freshwater aquarium fish you’ll come across are fairly hardy and can survive several degrees outside their comfortable range with minimal effect.

The only concern is for those of us that live in areas with bipolar weather, where winters are remarkably cold, and summers rather warm. Also if the heater in your aquarium room or fish tank malfunctions, it is a cause for concern.

But other than that, maintaining optimal temperature in a freshwater aquarium is a simple process. Please keep reading for more insight on what steps to take if your fish tank get too cold or hot for your fishes.

Fish Tank Temperature Control

Coming home to a bunch of floating fish because your tank is boiling or freezing is not an uncommon scenario, particularly for aquarium owners with little experience keeping tropical fish.

All it takes is a heater to remain on or off for a minute too long. Thus, I cannot emphasize enough how crucial controlling the temperature in your tank is.

But how do you do that?

That’s where a thermometer and controller, plus the positioning of your fish tank heater and maintaining a constant water level matters the most.

Aquarium Heater Controller

An aquarium heater controller is a device that allows you to regulate the temperature of your fish tank. The equipment is especially useful since heaters can be quite unpredictable, one day they could be working perfectly, and on the next day they be at best erratic.

An aquarium heater controller will keep the heater from boiling or freezing your tank, plus they come in different designs with some capable of a lot more.See this list by Cozy home of some of the best aquarium heater controller of 2020.

To work, a sensor probe inside your fish tank, the controller will read the temperature and compare it to pre-set temperature. If the tank is colder than the set temperature, the device will send power to the socket which will turn on the heater.

If the tank is too warm, the controller will turn the heater off.

Aquarium Thermometer

Aquarium thermometer is another small but essential item for your fish tank .

Having a good thermometer helps you keep track of your water temperature at various times and correct any problems resulting from temperature changes.

Over and above, a thermometer will aid in monitoring the heat distribution in an aquarium making sure there are no hot or cold spots in the tank.

Position Your Heater Correctly

Considering the right placement for your heater inside the aquarium ensure there is proper distribution of heat across your tank with no spots that are too hot or cold for your fish.

It is perfectly ok to place the heater horizontally or vertically, but by far, the best position is to place it at a 45°, though it depends on the type of heater you have.

Most people place it at the center of the back wall, but with more than one heater, I recommend place one on either side of your tank. Moreover, placing the heater in an area with

Use a thermometer to access how well the heat is getting distributed.

Keep Your Aquarium Water Constant

If you do not maintain the water level in your fish tank at a constant level, you will have massive temperature fluctuations in your fish tank. As much, doing large water changes in one go will make you lose control of your fish tank’s temperature.

For that reason, only do small water changes at any one time and make sure you refill your tank with water of the same temperature as that in your aquarium to the same level as before.

You also want to stay ahead of evaporation as this will lower your tank water level rather gradually you may even miss the change if not keen.

Position Your Tank Properly

The temperature of your tank can vary a lot depending on where you place, but most fish keepers don’t seem to realize this.

A tank by a sunny window or near a heater unit will heat up dramatically. Whereas an aquarium near a fan or air-con system may remain chilly even when you run your fish tank heater all day.

Therefore, make sure you position your tank in an area where the external environment least affects your aquarium’s environment. Ideally, place the tank in an area of the room that remains within the average room temperature reading for most of the day.

What To Do If Your Fish Tank Temperature is Too High?

It’s not uncommon for some places to get a heatwave during summer with temperatures topping 100°F, which affect fish as they do all other pets, albeit living in water.

So, how do you lower the water temperature in your fish tank?

Well, one thing that is good to note before you get to cooling your fish tank is that, at times, it’s not the high temperature that will kill your fish, but the fluctuations. So be really careful if you decide to cool down your aquarium.

That said, to bring the temperature down, begin by filling zip lock bags or water bottles with ice and let them float in your fish tank. Make sure you increase the surface agitation with bubblers (airstones) as well to help dissolve more oxygen in the fish tank as warm water holds less oxygen than cold water.

A fan blowing air across the top of your tank surface will also do the trick, but your water will evaporate at a much quicker rate. For that reason, be ready to top the water whenever the level gets too low.

If you decide to use cold water to cool your tank, I recommend doing this gradually to avoid shocking your fish and make a bad situation worse.

Of course, the only long term solution would be to get a chiller for your aquarium. It’s like a heater, but for air conditioning rather than heating.

Also appreciate that some tropical fish like guppies, angelfish, clown loach and mollies enjoy water as warm as 86°F and you may be worried a little more than you should.

Below are other hacks that’ll go a long way in lowering your fish tank temperature:

  • Shutting off your aquarium lights especially if nothing is keeping them from heating the water.
  • Increase your water change frequency, but instead of cold water, allow the water to reach room temperature, which will help lower the temperature at a much slower rate hence stress your fish less.
  • Feed your fish one or two times more in the day as the high temperature means a faster metabolism. While this trick will not lower the temperature in your tank, it will help your fish cope with changing environment better.

Tropical Fish Tank Temperature Too Cold

Cooler water fishes like goldfish will survive in water as cold as 62°F, but other species like betta and tetras need the fish tank to remain warm; at least 72°F.

This means if your aquarium temperature dips as it would in a winter power loss or when you forget to switch on the heater, your fish will be affected even though they may not necessarily die.

Nonetheless, anytime you need to choose between hot and cold, always go cold. Too hot means not enough oxygen for the fish and they do not do well.

Usually, cold water only means a minor discomfort as long as you get it right fairly soon. Usually, the shock problems show through parasites like ich, digestive, and balance issues

A tropical fish in cold water will be lethargic and inactive but will recover once the heater comes back on. Healthy bacteria will also be inactive, meaning your fish tank may be a tad filthy than usual.

What Temperature is Too Cold?

As I mentioned before, most tropical fish prefer temperature anywhere from 72°F. As such, any setting below that can be a little cold for your fish.

However, it does depend on the specific species you are keeping, what might be cold for discus is not necessarily cold for goldfish or white clouds.

When considering tropical fish that prefer things on the warmer side, 70°F is most likely too cold, but when looking after species that’ll survive in cold tanks, 58°F is as low as you can go. Though I highly recommend keeping your fish tank above 62°F to help your fish’s metabolism stay functional, plus keep beneficial bacteria in your tank active.

Tropical Fish Tank Temperature For Common Aquarium Fish

A question I hear quite often is regarding the temperature preference for precise tropical fish species, most of which are commonly kept in home aquariums.

For that reason, below are the tank conditions that a few popular freshwater tropical fish prefer.


  • Temperature: 72°F to 82°F (optimal range), 70°F to 86°F (survival range)
  • ph: 6.8 to 7.8
  • Water Hardness: dH 8 to 12
  • Ammonia: 0ppm, Nitrites: 0ppm, Nitrates: 10ppm to 20ppm


  • Temperature: 68°F to 74°F (Fancy goldfish), 60°F and 70°F (Common goldfish)
  • ph: 6.5 and 8.4
  • Water Hardness: dH 5 to 12
  • Ammonia: 0ppm, Nitrites: 0ppm, Nitrates: 10ppm


  • Temperature: 76°F to 80°F (Optimal range), 60°F and 70°F (Survival range)
  • ph: Neutral around 7
  • Water Hardness: dH 5 to 20
  • Ammonia: 0ppm, Nitrites: 0ppm, Nitrates: 10ppm to 20


  • Temperature: 76°F to 82°F (Optimal range)
  • ph: 8.0 to 9.0
  • Water Hardness: dH 10 to 25
  • Ammonia: 0ppm, Nitrites: 0ppm, Nitrates: 10ppm


  • Temperature: 72°F to 78°F (Optimal range)
  • ph: 5.5 to 6.8
  • Water Hardness: dH 2 to 10
  • Ammonia: 0ppm, Nitrites: 0ppm, Nitrates: 10ppm


  • Temperature: 75°F to 80°F (Optimal range)
  • ph: 8.0
  • Water Hardness: dH 15 to 30
  • Ammonia: 0ppm, Nitrites: 0ppm, Nitrates: 10ppm to 20ppm

Zebra Danios

  • Temperature: 65°F to 77°F (Optimal range)
  • ph: 6.5 to 7.2
  • Water Hardness: dH 5 to 19
  • Ammonia: 0ppm, Nitrites: 0ppm, Nitrates: 10ppm to 20ppm

Tiger Barbs

  • Temperature: 68°F to 80°F (Optimal range)
  • ph: 6.5 to 8.0
  • Water Hardness: 10 to 30
  • Ammonia: 0ppm, Nitrites: 0ppm, Nitrates: 10ppm to 20ppm


  • Temperature: 68°F to 82°F (Optimal range)
  • ph: 7.0 to 8.3
  • Water Hardness: 10 to 28
  • Ammonia: 0ppm, Nitrites: 0ppm, Nitrates: 10ppm to 20ppm

Cory Catfish

  • Temperature: 74°F to 80°F (Optimal range)
  • ph: 7.0 to 8.0
  • Water Hardness: 3 to 10
  • Ammonia: 0ppm, Nitrites: 0ppm, Nitrates: 10ppm


  • Temperature: 75°F to 80°F
  • ph: 6.8 to 7.8
  • Water Hardness: 3 to 8
  • Ammonia: 0ppm, Nitrites: 0ppm, Nitrates: 10ppm


  • Temperature: 76°F to 84°F (Optimal range)
  • ph: 6.8 to 7.8
  • Water Hardness: 3 to 8
  • Ammonia: 0ppm, Nitrites: 0ppm, Nitrates: 10ppm


  • Temperature: 80°F to 86°F
  • ph: 6.0 to 6.5
  • Water Hardness: 1 to 4
  • Ammonia: 0ppm, Nitrites: 0ppm, Nitrates: 5ppm


Below are two questions I come across quite often, which may have crossed your mind too.

Can Fish Die If The Water Temperature is Too High?

Yes, your aquarium fish can die if the temperature in your fish tank is too high, though it will depend on the fish you have in the tank.

The same way your discus or angelfish will suffer in a freezing aquarium, is the same way danios and other cool-water fish will struggle in a boiling tank.

What even worse, while cold water will affect your fish metabolism gradually and may take a while to kill them, a too-high temperature setting will reduce the amount of oxygen on your fish tank, and suffocate your fish.

That said, most fish will last in water temperature slightly above their optimal range, meaning cold-water fish can live in up to 78°F.

Some species like angelfish and discus will only start to die when the temperature goes beyond 88°F. While species like betta, guppies, and tetras will only show signs of distress above 84°F.

Is 82°F Too Hot For Tropical Aquarium?

Yes and No; It will depend

As I’ve stated throughout this article, some tropical fish can withstand a higher temperature range than others.

Therefore, while 82°F may be too hot for goldfish, zebra danios, white clouds minnows, and maybe tiger barbs, mollies, and platys. It is definitely not too hot for guppies, tetras, betta, and is in fact, within the preferred range of many cichlids including discus and angelfish.

Eddie Waithaka

Resident Content Creator and Marketer at AquariaWise who talks about aquariums and fish and aquascapes a lot.

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