Nano Aquarium Heater Guide


Heaters in a nano aquarium is very important, more so than your average sized fish tank. Since nano aquariums hold a smaller volume of water compared to standard sized fish tanks, they do not retain heat very well. Even if the room temperature fall, larger aquariums will retain the heat for an extended period of time. It may take hours for the water temperature to start dropping. However, in a small nano tank, the rise and fall in room temperature will have a more immediate effect on the water temperature.

As ectothermic animals, fish rely on the environment to maintain their body temperature. If the temperature of the water falls out of their desirable range, they could die. Even if the water temperature is within a desirable range, if there is a rapid fluctuation in the temperature, it could stress the fish.

Since nano aquariums are prone to temperature fluctuations, it is up to the fishkeeper to monitor and maintain the water temperature. Therefore, invest in a reliable heater for your nano aquarium. Don’t forget to get an aquarium thermometer as well.

Nano Aquarium Heater

What is Different about a Nano Tank Heater?

A heater for a nano aquarium needs to be the right size.

First, it must be the right size in terms of heating capacity, or wattage. The general rule of thumb is to get a heater with a capacity of 5 watts per gallon of water. If you have a small nano tank of 5-10 gallons, get a 50 watt heater. If you have a 15-20 gallon tank, get a 100 watt heater.

Second, consider the physical size and shape of the heater. If you have a nano tank, a standard heater may not fit. Find an aquarium heater that will fit. If possible, find a heater that is low profile. This will help maintain the aesthetics of your aquarium tank.

Do I need a Heater for my Nano tank?

Surprising as it may sound, not all nano tanks require a heater. Depending on where you live and what type of fish you wish to keep, you may or may not need an aquarium heater for your nano tank.

First, if you live in a temperate climate, you may not need a heater. Also, if you intend to keep fish that prefer colder water temperatures such as goldfish and white cloud mountain minnows, you may not need a heater.

However, if you intend to keep tropical fish, you will most likely need to invest in an aquarium heater. Many tropical fish prefer a water temperature of around 78 degrees Fahrenheit. Climates in most regions do not hold this temperature year round.

Main types of Aquarium Heaters

There are three main types of nano aquarium heaters, which are submersible heaters, immersible heaters, and pad heaters.

Submersible heaters are the most popular option for nano aquarium tanks. They are often placed on the aquarium wall with suction cups. Since it is submersible, it can be installed vertically or horizontally.

Immersible heaters are not fully submersible. The heating mechanism will be placed under the water level, but a portion of the heater must stay above the water. This means that you do not have to get your hands wet when you adjust the temperature level. However, you would have to make sure to turn the heater off during water changes because it will be exposed to dry air. If the heater is exposed to dry air, and it is left on, the heater may overheat and start to malfunction.

Pad heaters, or undergravel heaters, are common for small nano tanks under 5 gallons. They are designed to be installed on the very bottom of the aquarium. The temperature setting on these small pad filters are often preset. This makes it very easy to install. Simply place it underneath the aquarium gravel, and plug it in. There is no need for calibration.

What size of Aquarium Heater do I need?

When choosing the right size for your aquarium heater, the general rule of thumb is to get approximately 5 watts per gallon of water. While this is only a general guideline, it can be useful when trying to estimate the wattage requirements.

When sizing the heater size for your tank, various factors are taken into consideration.

  • Volume of water (size of tank)
  • Temperature of room
  • Amount of heat retained in the aquarium
  • Heat output variance depending on different heater manufacturer

Below is a chart which provides a starting point for choosing the correct heater size.

Tank SizeTo heat by 5° CTo heat by 10° CTo heat by 15 °C
5 Gallon25 watts50 watts75 watts
10 Gallon50 watts75 watts75 watts
20 Gallon50 watts75 watts150 watts

Best Nano Aquarium Heaters

There’s a lot of different nano aquarium heaters on the market. Having many options is good, but it can make it difficult to choose the right heater. Here’s a few suggestions that we have for your nano aquarium, based on the size.

Best Nano Aquarium heater for tanks of sizes 1 to 2.5 gallons

Marina Compact

If you have a very small fish tank, then this may well be the heater for you. This is one of the smallest heater on the market with a temperature control.

Out the box it is set for 78° F which is the ideal temperature for most tropical fish. Once the temperature in the tank exceeds this the heater automatically switches off and switches back on once the temperature has dropped below this mark.

It is a fully submersible design and has discreet lines, making unobtrusive in even the smallest of tanks.

Best Nano Aquarium heater for tanks of sizes 2 to 5 gallons

Hydor Theo

The smallest adjustable heater on the market is the Hydor Theo. It is adjustable from 19 – 33° C with a simple twist of a dial. It is a fully submersible heater and is available in 25W and 50W, both of which are only 7 inches in length.

In recent tests conducted by a fish lab, it was found to maintain temperatures to within 1° F of its selected setting. A crucial benchmark for any nano tank heater.

Due to its small size and the fact that it is fully submersible, this little heater can be placed almost anywhere in your tank.

Best Nano Aquarium heater for tanks of size 6 to 10 gallons

Cobalt Neotherm

The Cobal Neotherm is an awesome aquarium heater for nano tanks. However, this it comes in various sizes, and it is one of the best aquarium heaters for fish tanks of all sizes.

Measured accuracy has shown that it stays within 0.5° F of its set temperature, which is remarkably accurate.

This is another fully submersible aquarium heater, so the installation options can be very versatile.

Tips for Using Aquarium Heaters

Understanding the heating requirements for your fish tank and choosing the right aquarium heater is important. However, it is also important to understand how to use it. Here’s a few tips on how to use your aquarium heater:

  • Always unplug your heater when changing the water. If the heater is left on while exposed to air, it can overheat and break.
  • Install the heater where there is adequate water flow. For example, placing it near the outflow of your aquarium filter. This will allow the heat to properly disperse throughout the aquarium. If the heater is place in a stagnant area, the water temperature may fluctuate throughout the aquarium.
  • Use a thermometer to keep an eye on the water temperature. Many heaters do have a temperature reading on the unit, but do not rely on this alone.

Fish Laboratory

With decades of collective fishkeeping experience, we are happy to share the knowledge that we've picked up along the way. Our goal at Fish Laboratory Aquatics is to keep publishing accurate content to help fishkeepers keep their fish healthy.

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