Our subaquatic friends are cold-blooded creatures. It’s a bit difficult for us to understand what this is like, being warm-blooded ourselves. We can create our own heat within our bodies, which allows us to adapt much better to cold temperatures. Fish, on the other hand, don’t have this privilege. They depend on us to keep their environment the proper temperature. allowing them to remain comfortable and, ultimately, alive.
Here we will examine all the basics you should know about heating the aquarium to give you the greatest success in maintaining a safe and secure water temperature.
Table of Contents
Factors of the Temperature Equation
The first thing to determine is how much power, measured in watts, you will need to heat the water and maintain it at the proper level.
What is the proper level? This depends on the types of life you’re keeping in the aquarium.
A saltwater aquarium is usually kept in the range of 76-82 F (24-28 C).
A freshwater aquarium is close to the same, generally targeting around 75-80 F (24-27 C).
It is important not to assume based on generalities, though. Some fish are coldwater fish, and enjoy temperatures much lower in the 60’s F, whereas some live in warmer environments. Take a few minutes to research your particular fish life to see what is an ideal temperature range. Most heaters can keep water within 1-2 degrees F of the target, so be sure to aim for something in the middle of the comfortable range for your fish.
Once this target temperature is known, you’re ready to consider the factors which will determine the power of your heater.
Room Temperature
Take the temperature of the room in which your aquarium will be placed. It’s best to take this temperature in the coolest part of the day, usually very early morning around 5 AM. At this time, how many degrees will your heater need to raise the water temperature above room temperature?
For example, if you find the room temperature is 68 F, and you’re targeting a water temperature of 78 F, then your heater will need to raise the water temperature by 10 F.
Surrounding Influences
Sometimes, surrounding influences can have a direct effect on water temperature, which may overpower the room temperature.
This could include being placed in direct sunlight, sitting near a draft like an air conditioner or air heater, or being near a machine which puts off its own heat. If you’re unsure how this is likely to influence the water of the aquarium, take the temperature of unheated water in the same location.
Height from Floor Level
If you have a multi-story home or office, placing the aquarium on an upper floor may mean it is in a hotter environment than the downstairs rooms. Heat rises, so even the height of the aquarium from floor level can have a minor effect on its temperature. While this may not be as big a factor, it’s still something to consider especially if you are trying to heat two aquariums at different levels.
Other Aquarium Equipment
Other machinery such as a canister filter can also heat the water to a small degree. So you may not need as much heating power as you otherwise would in the absence of other equipment that offers small heat as a biproduct of its main function.
Water Volume
What is the water capacity of the tank you are planning to heat? If you’re unsure, it’s easiest to measure in liters by using the following measurements in centimeters:
(Width x Height x Depth) / 1000
Be sure to measure height only to the water level.
The answer to this equation gives you the number of liters that require heating.
For every 1 liter of water, you will need 1 watt of heating power.
If you prefer to work with US gallons, then know that 1 gallon is approximately 3.75 liters. So if you have a 20 gallon tank, the equation is (20 gallons x 3.75 liters-per-gallon) = 75 liters. This means 75 watts is the minimum power that you should have in heating power.
Important note: The above equation applies to water that needs to be heated 10 F or less above room temperature.
For every 5 degrees above 10 F that needs to be heated, add 50% of the original wattage requirement.
For example, if you have a 50 gallon tank (190 liters) in a very cold room and need to heat it 20 F above room temperature, then here is the equation:
190 liters + (0.5 x 190) + (0.5 x 190) = 380 watts needed
It’s important that for larger aquariums, usually 50 gallons or more, it’s best to use multiple small wattage heaters that add up to the required wattage instead of one all-powerful heater. This reduces the risk of the single heater causing a disaster due to malfunction, and it also allows you to have a backup heater in case one of them goes out.
Heating Materials
Aquarium heaters can be constructed of a number of different materials, which we will examine next.
Glass
This is often the cheapest option but also has the potential to crack or shatter, which can leak water into the heater. It doesn’t have as much heating power as other options, but it can be ideal if you’re looking for something economical and for a small to medium-sized tank.
Plastic
While not as popular, there are some heaters made of highly durable plastic. These also tend to be a cheap option with the added benefit that they won’t shatter or crack like glass.
Stainless Steel
These types are cheap and durable, and they also hold heat better than glass. This means better efficiency and less use of electricity over time. While there have been reports of some heaters exploding as a malfunction, this is quite rare especially as technology has improved. So long as you keep the heater submerged in water, and don’t forget to turn it off when cleaning the tank, chances are you will not have significant problems with overheating.
Titanium
Like stainless steel, these types are more powerful in their ability to heat in comparison with glass or plastic. The fact that they don’t crack and leak can make them much more durable as well. Titanium alone does not rust, unless it is mixed with another metal. The main risk, as with most heaters, is overheating. If you notice a calcium buildup on the heater, just be sure to clean it (turn it off first!) and make sure to eliminate that obstacle for the heat to evenly escape.
Quartz
A heater made of quartz is corrosion and shatter resistant. These generally come with a protective casing to protect fish from direct contact with the heating element. They are not materially more expensive than glass or plastic heaters.
PTC (Positive Temperature Coefficient)
The most recent development in heating technology is known as PTC, designed using ceramic materials. The benefit to this type is that it is designed to avoid overheating even if the heater is exposed to air (not fully submerged) or becomes covered in debris. It self-regulates its temperature in the midst of doing its primary job, which is to heat the water to the target temperature. This is more expensive because it is cutting edge technology.
Heater Types
Hang-On
The hang-on heater does exactly that: it hangs over the side of the aquarium wall into the tank. Because these are placed vertically in one part of the aquarium, they tend to be best suited for small- to mid-sized aquariums. If you have a larger aquarium, the heat distribution from these may not be effective. You then may need to consider acquiring a second heater or simply going with a different type which distributes heat more evenly. Note that you will want to pay special attention if using one of these, because if water evaporates and goes below the minimum water line for this heater, there is a risk of overheating and/or breakage.
Submersible
The heaters that can be fully submersed underwater also have greater power to heat the aquarium evenly. Why? Because they can be positioned either diagonally or horizontally, usually closer to the bottom of the tank. Because of the better heat distribution, these can be used to heat larger tanks than hang-on heaters. They are affixed to the aquarium sides with suction cups to hold them in place.
Inline External
Want to hide your heater altogether? If you use an external filter like a canister or sump, then you can use an inline heater to heat the water on the way back into the aquarium. This is essentially a heated pipe. It can more evenly distribute the heat because of the flow of water being dispersed back into the aquarium. The main risk is that if the water pump breaks down, this means no warm water is flowing into the aquarium. You would want a backup heater (not inline), as you should have in any case, for emergency situations.
Heating cable
Another heating method that is hidden from view is one that is placed beneath the substrate. The warm water under the substrate creates a slight current in reaction with the cooler water above it. This can benefit plant life, but at the expense of possibly having the plants take root around the cables, making it difficult if not impossible to remove plants safely if needed. This method of heating is more expensive and has also fallen out of popularity due to lack of evidence for effectiveness.
Heater Placement
There are three things to keep in mind when placing a water heater.
- If you have a submersible heater, place it horizontally or at a 45 degree angle near the bottom of the aquarium, about 2-3 inches above the substrate.
- Along the bottom, place it closest to a high circulation area. This could be above a bubble wall or near the filter outflow / inflow. If you have the option to place near the filter outflow, this might be slightly preferable to the inflow so as to avoid risk of overheating beneficial bacteria in the filter.
- If possible, place it in a hidden spot, or design a hiding place such as a plant or decoration to cover it.
There is some debate over how to position a heater, particularly whether it should be 45 degrees or horizontal. Both have good points. The 45 degree angle allows the heated water not to flow up directly to the heat sensor (as it would in a vertical position), causing it to think the general water temperature is higher than it really is. This also allows water on multiple levels to be heated at once. The horizontal position allows a greater length of heating effect, which of course rises throughout the rest of the aquarium. The horizontal option also tends to have a better visual aesthetic rather than a “crooked” heater on the back of the tank.
Last but certainly not least, make sure that the heater is not in contact with anything in the aquarium except the water.
Conclusion
No matter which type of heater you choose for your aquarium, it is always advisable to keep one additional heater on hand in case of an emergency. Nothing lasts forever, and that means your heater will sooner or later go out. If you have a temperature alert system for emergencies like this, you can avoid a catastrophic event for your fish by replacing the heater immediately with your backup. If you have more than one heater in operation, then this diversifies the risk. With regular attention, appropriate preparations, and following safety precautions, you limit the risks involved with heating mechanisms and provide your fish with a comfortable temperature to live in. They’ll warm right up to their new home!