The Best Small Fish Tank Heater – Small Aquarium Heaters

A small fish tank heater is good for tanks with a volume up to 10 gallons.


It is important to provide the right requirements for your fish to survive and thrive. Not having the correct water temperature can cause great stress to your fish leading to a shorter life span. If the conditions are not optimal, wrong water temperature can easily lead to death if not quickly remedied.


I lost one of my favorite fish a couple of years ago because my aquarium heater became unplugged and I did not notice. You read about my beloved Little Moe in this Fish Tank Thermometer article.


But let’s get into what you came here for: the best small fish tank heaters.


best small fish tank for bettas


The Best Small Fish Tank Heater


Here are a few basic pointers to keep in mind when thinking about small tank heaters.


Important to remember:

  • Only turn an aquarium heater on once it has been placed into the water
  • Get a covered fish tank, or make a cover for your tank to help trap the heat in – it can be hard to reach and maintain temperature with an open tank
  • If you need to remove a heater from the water, switch it off and let it cool for a while before removing it from the water


Let’s see the recommendations.


1. Tetra HT Submersible Aquarium Heater With Electronic Thermostat

best small fish tank heater for aquariums


The Tetra HT Submersible Aquarium Heater is the best small fish tank heater. It can be purchased in either 50 watt (model HT10) or 100 watt (model HT20). Both options are best used for tanks with a volume of between 2 and 10 gallons.


Your choice of model will depend on factors such as the ambient temperature in your house and the size of your tank. If you live in a cold climate, keep your house rather cool, and have a 10 gallon tank, you should consider getting the 100 watt model. But for most other scenarios the 50 watt heater will be the perfect choice.


This is a small water heater which can be easily concealed behind your tank decorations and plants. The 50 watt model is approximately 5 inches long, while the 100 watt model is just over 8 inches long.


Features of the Tetra heater:

  • This is a fully submersible fish tank heater that is attached with a suction cup to the inside of the tank
  • It can be installed vertically, diagonally, or horizontally – as long as it is under water it will function
  • Lights to indicate when the heater is reaching temperature (red) and when water has reached the set temperature (green)
  • Automatically set to heat to 78° F with an in-built electronic thermostat – the temperature cannot be changed
  • Automatic shut-off feature in the event of an electrical short
  • Approximately 5 foot long power cord


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2. Uniclife Submersible Aquarium Heater 25-50W with Thermometer

best small fish tank heater


The Uniclife Submersible Aquarium Heater is an adjustable heater with a thermometer. The temperature can be set between 61°F and 90°F (or 16°C and 32°C). Most aquarium fish need a water temperature of between 76°F and 80°F. Check out some more specific temperatures for different fish down below.


This heater comes in two models –  a 25 watt and a 50 watt. The 50 watt heater is going to be sufficient for the major majority of fish tanks up to 10 gallons. The 25 watt model is great for 5 gallons and less.


The thermometer that comes with this heater is a sticker. It can be peeled off and stuck onto the side of your fish tank.


Features of this small fish tank heater:

  • Made of shatterproof glass
  • Double insulated heater
  • Temperature dial on the top of the heater
  • Automatically switched on and off to stay at the correct temperature
  • Can be placed horizontally, vertically, and diagonally in the tank
  • 1 year explosion proof warranty


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3. Marina Betta Submersible Heater for Aquarium

best small fish tank heaterThe Marina Submersible is a very small Betta fish tank heater. This is only an 8 watt heater that is suitable for up to 1.5 gallons of water. This heater is always on and has no thermostat. It would be a good idea to get a thermometer to go with this small heater. As with most fish, Bettas prefer a tank temperature of 78 degrees.



  • Fully submersible for small tanks
  • Made from durable polymer
  • Automatically reaches set temperature



Best Temperatures For Aquarium Fish


The standard assertion is to set your tropical fish tank temperature to 78°F. There are some fish that like a few degrees warmer or cooler, but you should generally set your heater to 78°.


Here are the temperature requirements for some of the most common aquarium fish:

  • Bettas (Siamese Fighters) –  between 78° and 80° F, and never below 74°
  • Tetras – between 72°F – 78°F – will likely become stressed at higher temperatures than 78°
  • Discus – between 82°F – 88°F – should not be kept with fish that need slightly cooler temperatures
  • Chiclids – between 72°F – 82°F
  • Oscars – between 74°F – 81°F – require a constant temperature to remain healthy & well
  • Rainbows – between 80°F – 86°F – as they prefer higher temperatures they go well with Discus fish


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