How Long Does It Take To Heat The Average Fish Tank

What fish can live together? What size tank do I need? Which filter system is the best? How often do I clean my fish tank? These are a very small handful of questions that people ask when they want to purchase a fish tank for the first time.

People tend to think it is easy until they start researching and purchasing everything you need. There is a lot more to it than a fishbowl, some rocks, and a fish. One of the biggest factors is the temperature of the tank. 

How Long Does It Take To Heat The Average Fish Tank? Depending on the fish that you have in your aquarium, you are going to want your temperature to be between 76 degrees and 80 degrees. For “cold-water” fish it will need to be at 70 degrees or less. 

The amount of time that it will take to get your tank to the average temperature will depend on a few things; where you set up your tank, the temperature in the room, and the temperature that you put in the tank when you fill it. 

Fish Tanks-What You Need To Know

There are a large variety of fish tanks on the market. They range in size from the basic fish bowl (if you consider that a tank) all the way to 100+ gallons. Depending on how many fish you want and the size of the fish is going to determine what size of fish tank you need to purchase.

The general rule of thumb; you need 10 gallons of water for every 2 inches of fish. There is a slight exception to that. If you just want guppies, you can easily have 4-6 in a 10-gallon tank because they are so small.

They still have plenty of room to swim around and space to not be crowded in the tank. But, for some other fish, it is highly recommended that you follow that rule. It will aid in keeping the fish healthy and your tank in good condition.

Glass vs. Acrylic Aquariums

This is not only going to come down to personal preference but also your budget. The acrylic fish tank is going to cost you more than a traditional glass fish tank. Both styles have their own pros and cons, so you will need to do some research if your finances allow for an acrylic tank.

You can read this article: How To Clean An Acrylic Aquarium that I wrote about it.

Acrylic tanks are better insulators, won’t break as easily as glass tanks, and are more lightweight.

Your glass aquarium will be a little easier to maintain, as far as cleaning the outside (and inside) walls. You don’t have to worry about easily scratching your glass tank, you don’t have to worry about potential yellowing of your tank, and they are more budget-friendly.

Fish Tank Shapes

Glass tanks basically come in one shape, rectangular. Acrylic tanks, on the other hand, come in a wide variety of shapes; octagon, pentagon, spherical, hexagon, and more. This is because acrylic is easy to manipulate. So if you want to have a real unique and eye-catching tank, go for acrylic. Again, it will come down to personal preference and more importantly, your finances. 

Average Fish Tank Size

As mentioned earlier, there is a very wide variety of sizes of fish tanks that you can buy.

On average, most people will purchase a 20-30 gallon tank. This allows you 2 to 3 fish, depending on the size.

You want to make sure your fish have enough room to grow and to swim around comfortably. This will keep the fish happy and healthy and also aid in having a healthy environment for them to live in.

If you are choosing a larger fish species, you may only be able to put 1 fish in your 20 gallons and 2 fish in your 30-gallon tank. You want to decide on the fish, when they are adults, not babies. If you choose a tank when your fish are babies, they will outgrow the tank, and you will be purchasing another one. So, find out how big the fish are going to get, and then decide on how many you want and then purchase the correct tank size. 

Heating An Average Sized Tank

The average temperature in any size tank is 76 degrees to 80 degrees, for most tropical fish. There are, however, “cold-water” fish who thrive on temperatures at 70 degrees or less;

  • Goldfish
  • Zebrafish
  • Guppies
  • Rosy barb
  • Gold barb
  • Paradise fish
  • Rainbow shiner

There are many others as well. This means you are not required to have a heater in your fish tank. The temperature of your home should keep the water temperature just where you need it. For warmer climates, you may even have to have a fan, especially made for fish tanks, in the summer months.

Reaching and Regulating Fish Tank Temperature

The rule and recommendations here; fill your tank with lukewarm water. This makes it easier on your heater because it won’t have to work as hard to bring your tank up to the optimum temperature. 

It is also recommended to let your tank sit for 24 hours after you install and turn on the heater. Before you put your fish into the tank you, of course, check the temperature. This ensures there is no unnecessary shock or stress to your fish. 

You want to place your heater near the maximum water flow. Either the inlet or the outlet from the filter. Having your water flow directly past the heater guarantees quick and evenly dispersed heated water. 

The temperature should remain constant if you don’t fluctuate the temperature in the room too much, and if your heater is working properly. Most heaters have built in thermometers, that will shut off when the water temperature reaches the maximum that you set.

It also helps to set the fish tank lights on a timer, 10-12 hours at a time. Depending on the bulbs used, the water temperature can be affected. An acrylic tank will hold the temperature at a more consistent level because it is a better insulator.

But you have to make sure your lights contain NO UV rays, or it will yellow your acrylic, over time. Having an optimal thermometer will also aid in making sure your tank temperature stays regulated.

To help regulate the temperature do not place your tank directly in front of a window where the sunlight can hit it. You also do not want to place it too close to your air conditioner or any vents, because it could change your water temperature dramatically. There is an aquarium heater controller that makes regulating the tank temperature a breeze.

Fish Tank Heaters-5 Main Types

There are 5 main types of heaters; hanging, submersible, in-line, substrate, and filter. The hanging filter and the submersible are the most popular of the 5. 

HangingJust as the name suggests, this heater hangs on the top of your fish tank. There is a glass tube that encases the heating element.
This is all that will sit in the water. Your tank hook will have to have a hole in it, for the heater. This type normally comes in the “starter kits” for fish tanks.
These are usually less efficient, but do provide basic heating and doesn’t take up tank space.
SubmersibleThese sit under the water and are the ones that you want to set-up next to your filter inlet (or outlet).
Most of these will have an LED light on them, to indicate when they are running.
If you ever see the light off for a long period of time, you should check the water temperature, in case something has gone wrong.
The submersible heaters are more efficient at keeping our tank at a consistent temperature.
SubstrateThese are typically wires that are fixed onto the base of your fish tank and are used in conjunction with another type of heater, usually the submersible.
These are not very common anymore and they can be quite spendy.
In-LineThese are normally hooked up between the sump or the filter so that the water is heated up as it flows back into the tank.
Made of heatproof plastic and used with bigger fish, like the Oscar, who is aggressive and loves to fight with fish tank equipment when they get stressed or agitated.
These are a lot more expensive than the other heaters but may save you money in the long run if you have aggressive fish. 
Filter HeaterThese are filters that will have the heating element built into them.
As the water passes through the filter it is heated up. Typically they are found in canister filters and some chosen power filters.

5 Best Aquarium Heaters

The optimum aquarium heater will heat your tank safely and uses a controller that keeps it in the perfect temperature range for our fish. You need to purchase the correct heater for your tank size. You don’t want a large, power heater in a smaller tank and visa versa. All heaters will tell you which size of the fish tank they work best with.

You also have to take into account what type of tank you have; saltwater, freshwater, betta tank, reef tank, or turtle tank. The manufacturer will always state where their heaters can be used. You can also find tank heaters that will work for various types of tanks. A versatile option is less stressful than searching for a specific option.

Recommended Thermometers For Aquariums

There are many heaters that have a built in thermometer, but it never hurts to have 2 in the tank or a spare one on hand. Here is a quick list of some of the best thermometers for your fish tank.

There are many many other types and styles of aquarium thermometers out there. I could spend all day listing them and telling you about them. Myself, I prefer a thermometer that goes inside the tank. I believe they are more accurate than the ones that hang on the outside of the tank because they don’t actually touch the water. 


There are many sizes of fish tanks on the market. There are also many shapes to choose from, if you choose an acrylic tank. The average size of a fish tank that most people choose is the 20-30 gallon fish tank. It is not too big for first time fish owners, but it also is more than just a bowl and a fish. 

It is recommended that you fill your fish tank with lukewarm water and leave it to sit overnight or for 24 hours. This will help your heater warm the water up quicker and it will not have to work as hard to get it done. Make sure you check the temperature before you put your fish in, just to make sure it is correct. You do not want to add any undue stress to your fish by placing them in a tank that is too cold or too hot. 

All manufacturer’s packaging will tell you what size aquarium the filter is optimum for, the maximum temperature that it will go up to, and a lot of other pertinent information. Make sure you read them closely so that you are getting the heater that is perfect for your set-up. Check the temperature periodically, and always keep an extra thermometer on hand. 


I'm passionate about fish pets and love sharing everything I learn about them.

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