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Top Fin® Heater Setup and Adjustment

By and large, most fishkeeping hobbyists use an all-in-one submersible aquarium heater to achieve, and maintain, the best climate for pet fishes to live and grow.

This help guide explains how to set up a fish tank heater and then adjust the settings to create the ideal amount of warmth for various fish families and different tank sizes.

Top Tips for Setting the Heater Temperature

Before you start fishkeeping for a hobby, there are several factors that you should consider, especially:

So, unless you buy one of the Top Fin fish tank kits, you may need to buy the accessories as separate items (including a water heater).

Either way, you'll need a comfortable environment with a stable water temperature. This will be paramount for the health of your fish and any live plants that you put inside the tank.

In fact, maintaining the optimum aquarium temperature is also important for efficient oxygenation. If the water is too cold or too hot, it can cause the premature death of beneficial bacteria. It can also cause a chemical imbalance which often results in poor metabolism for most tropical fish species.

Installing a Submersible Aquarium Heater

There will be a thermostat to help you control the temperature of the water. So, before you plug it in, check that it has the correct setting for your particular requirements.

After you have set the temperature on a Top Fin aquarium heater, affix it to the side wall of the tank (e.g. using a suction cup) and insert the plug into a power outlet.

Make sure the tank has enough water to surround the heater. Plus, check that the electrical cord is not tangled and it's not dangling in any other water sources nearby.

This part is important:

You should see a red indicator light on the front of a submersible aquarium heater. This means the heating element contained inside the unit is working. In other words, it has started to heat up the water inside the aquarium.

It is best to monitor the heater for up to an hour as it warms up the water inside the tank. Soon, the indicator light should change from red to green after it reaches the desired water temperature (e.g. as shown on the thermostat dial).

Using a Top Fin® Aquarium Heater

It's important to use a water heater with enough electrical power to cope with the size of aquarium that you have. Fish tank heaters made by Top Fin Spectrum Brands are available in two (2) different sizes:

In general, the best place to put an aquarium heater is upright on the side of the tank and close to the air pump and filter.

This placement encourages water to circulate with an even heat distribution around the container as it generates warmth for the fish.

Pro Tip: Another help guide explains how to troubleshoot Top Fin filter problems with expert tips for finding easy solutions.

Manufacturer Operating Instructions

The Top Fin all-in-one compact submersible power heater is already preset at a temperature of 25° Celsius (77° Fahrenheit). This setting assumes the maximum difference between ambient and preset is less than 5° Celsius (41° Fahrenheit).


  • Below an Air Conditioning ventilation system
  • In direct sunlight or near a heat source (e.g. a central heating radiator)
  • Under a light source if it will be on for extended periods of time

The heater is for underwater use only. Do not use it when it is dry or partially dry because it may reach a temperature in excess of 80° Celsius (176° Fahrenheit) which can cause skin burns.

Pro Tip: For the most part, Top Fin aquarium heaters will be able to raise the temperature of the water by one (1) or two (2) degrees Fahrenheit per hour. They are reliable water heaters that are easy to use and made of shatter-resistant quartz glass for additional safety.

How to Adjust Top Fin Heater Temperature

Most fish species kept as pets in captivity will be healthy when the water is stable at 22-26° Celsius (around 75° Fahrenheit). So, you may only need to install a preset aquarium heater in the correct position, turn it on, and test it for proper function.

Even so, because Top Fin heater units are user-friendly, you will be able to fine-tune the temperature of the water according to your needs.

But, what if you find the heater is not providing enough heat or it feels cool to the touch? In this case, there are ways to adjust the thermostat setting to increase the heating power (or reduce it).

You should be able to rotate the button or knob if yours is an adjustable heater. But, you may need to replace the entire unit for one that is set to the desired temperature if you have a non-adjustable version.

How to Set and Adjust the Temperature on a Top Fin Aquarium Heater?Best water temperature range for popular fish species:

Pro Top: Often, the water temperature in aquariums will fluctuate through the day and at night-time. This is one reason why aquarists use a thermometer to check the water temperature at regular intervals.

How to Use a Fish Tank Thermometer

You can use the Top Fin thermometer or the simple sticker version to measure the temperature of the water inside the tank. In simple terms, this simple device helps you monitor and regulate the heat inside your aquarium.

The Top Fin® digital aquarium thermometer has an LCD screen that displays in Celsius or Fahrenheit and it comes with a replaceable battery.

Keep in mind that it's best to place it at the opposite end to the heater position so you get accurate temperature readings.

How to Check if the Top Fin Heater is Working?

After following the manufacturer's instructions for Top Fin heater setup and adjustment, what can you do if it's not heating the water? Here are some basic steps to take when troubleshooting the problem:

Pro Tip: The type of fish that you are keeping will determine the ideal water temperature inside the tank. Even so, heating the water above 30° Celsius (86° Fahrenheit) for a long period of time may harm the fish.

Related Information and Help Guides

Note: The short video tutorial [4:11 seconds] presented by 'Fred's Reviews58' explains how to use the 100 watt Top Fin H100 aquarium heater.

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