Mini Aquarium Heaters

Introduction

I’m often asked and I see numerous questions on the web regarding mini aquarium heaters to heat tanks as small as one US gallon (~3.8 Litres ) of water. This question always makes me worry. There are mini aquarium heaters out there however they are addressing a heating issue in a fish tank that will certainly be running into problems.

Are small fish tanks easy to look after?

The best way to look at this question is to consider the amount of water in the ocean or a river. The quantity of water is so large that the temperature is stable and other factors such as PH and salinity are stable as well. Introduction of heat from the sun on a hot day will have a gradual warming effect, so gradual that it will only affect the surface water. Contrast this to the miniature aquarium with only one gallon of water, switching on your small and low powered mini aquarium heater has the potential to raise water temperature by a number of degrees in only minutes. Likewise with water changes, replacing half the water will have a drastic and immediate shift in temperature.

I recommend a minimum aquarium size of five gallons (~20 Litres ). This is also a good size to use as a nursery or fry raising tank.

Why are these rapid changes bad for our fish?

Fish are processing the aquarium water through their bodies constantly. Sudden and drastic changes in water parameters are bad news for all fish and dependent on the severity they invoke temporary shock or leave permanent damage. Shock can also lead to less resistance against diseases such as white spot.

Recommended heater size for your mini aquarium

Assuming your mini aquarium is 5 US gallons you should be comfortable in most climates using a 25 Watt heater. Here is a rough guide to heating as you increase the volume of water:

• 5 Gallons / 20 Litres = 25 Watt (Mini) Heater
• 10 Gallons / 40 Litres = 50 Watt Heater
• 25 Gallons / 100 Litres = 75 Watt Heater
• 40 Gallons / 150 Litres = 100 Watt Heater

If your living in a particularly cold climate where your tank will need to heat the water 10 degrees Celsius or 18 degrees Fahrenheit above the air temperature then select the next higher rated heater in the table.

Selecting your mini aquarium heater

I’ve researched a number of the lower rated and miniature heaters for this article however I can’t recommend anything other than the Jager 25 Watt aquarium heater as the smallest heater to use. (Note that I have no association with Jager/Eheim) With a background in electronics and many years of experience working with aquariums the Jager makes me feel safe putting my hands into the water (although we know the heater should be turned off first I don’t know anyone that does), the Jager uses laboratory quality glass and incorporates a number of safety features. They are now the only heater I use and I can’t recommend highly enough.

In summary, my recommendation for a mini aquarium is a minimum of 5 US Gallons and a 25 Watt Jager Heater.

Good luck and have fun!

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