An aquarium heater is to keep the water temperature of a fish tank at a stable, desired level. It is an essential equipment if you have or plan to have tropical fish.
Do I need an aquarium heater for my fish tank?
As long as you have tropical fish, there is no doubt that you need a heater for your fish to thrive. Otherwise they will be sick or even die. If you do not want to get a heater, please do not get any tropical fish because they will not live for long.
Why do I need an aquarium heater?
Depending on the actual species, most tropical fish must live in water at temperatures of 74~82F (about 23~28C) in order to survive. When the water temperature is below the ideal level, some tropical fish will become inactive and even refuse to eat. Before long, these fish might starve to death if not frozen to death first. Even if your fish will still eat, in the long run, lower than ideal water temperature can weaken their immune system. Weaker immune system will cause the fish to become sick and die.
My room is warm enough now. Do I still need a heater for my aquarium?
Unless you live in a tropical area, you will always need a heater for your tropical fish aquarium. In most areas, the hot summer might provide high room temperature to keep the aquarium water warm enough for the tropical fish during the day, but at night the room temperature might be a lot cooler. Likewise, if you do not live in a tropical environment, it is unlikely that you have a high enough room temperature all year long. The limited water in an aquarium can cool down at a rapid rate when the air temperature is low. Tropical fish dislike large swing of water temperature, because it can shock and kill them.
Will an aquarium heater overheat the water in a fish tank?
No, unless it is malfunctioning or if you have the wrong settings, all aquarium heaters are designed to automatically turn off when the desired temperature is reached. They will automatically turn on again when the water temperature is getting cooler than what you set.
Tips for Choosing and Using an Aquarium Heater for Your Fish Tank
1. Not all aquarium heaters are submersible
Please check the specification carefully on the heater. While some of them can be completely submerged, others have a marked water line for you not to have the water above it. We recommend everyone to use full submersible heater for your aquarium. Once again, check the specifications when you buy.
2. Not all aquarium heaters are adjustable
While some aquarium heaters give you the freedom of setting a temperature by yourself, some cheaper low model heaters have only one stock setting and it can’t be changed at all. Those non-adjustable heaters will always have the same temperature setting on them, and it is recommended to buy adjustable heaters so you have the freedom and option to set your own water temperature.
3. Always use a thermometer with the aquarium heater
Do not trust the settings on the heater. Even for the most reputable brands, some exactly same model of heaters might result in different water temperatures when you have the same setting. It requires you to monitor the actual water temperature with a thermometer and adjust the settings on the heater accordingly. The thermometer should be placed on the opposite side of the aquarium heater in a fish tank to get a more accurate reading of the water temperature.
4. Do not let the water go below the minimal water line on the aquarium heater
While some non-submersible heaters have a line for you to keep the water below it, all aquarium heaters also have a line for you to keep the water above it. If the water does not reach this minimal level, the heater will remain on because the air around it is cooler. Due to the fact that the air cannot transfer heat as quickly as water, the heater will quickly burn itself out if it is exposed in the air while it is on. This is more likely to happen during a water change for the aquarium, and it is recommended to turn the heater off before a water change to avoid damaging the heater as well as a possible electrical shock.
5. An aquarium heater should be installed near where there is a good water flow
Although water can transfer heat fairly quick, a large aquarium without a good water flow can still result in an uneven water temperature in different parts of the fish tank. It is unhealthy for the fish. You should always have good water current in your aquarium, and the best place to install the heater is near either the intake or the outflow of your filter system. You may also place an air stone directly below the heater to have the air bubbles bring the water up around the heater.
6. Too low or too high wattage aquarium heaters are not suitable
All aquarium heaters have the manufacturer recommended tank size rated on them. When a heater does not have high enough wattage, it might never bring the water to your desired temperature.
Typical Aquarium Heater Specifications
Below are some of the typical aquarium heater specifications (They can vary for different brands.):
50 watt for fish tanks of 7~15 gallons
75 watt for fish tanks of 15~20 gallons
100 watt for fish tanks of 20~40 gallons
150 watt for fish tanks of 40~75 gallons
200 watt for fish tanks of 75~105 gallons
250 watt for fish tanks of 105~150 gallons
300 watt for fish tanks of 150~250 gallons
The above shows that manufacturers recommend 2~5 watts for each gallon of water. One thing I have noticed though, is that lack of wattage can be compensated by good water current in the fish tank to a certain point. Once after I had replaced my EHEIM Jager Aquarium Thermostat Heater 100W with a Rena SmartHeater Aquarium Heater 50W in my 40 gallon aquarium (because the Jager was too bright for my aquarium’s black background), the water temperature was stable because of the good water flow. The only difference is that the 50W heater has to stay on for a longer period of time than the 100w.
Of course if the fish tank is way too big for the heater it will not work. For example, if you use a 50w heater for a 180-gallon or even 250-gallon tank, it might still not be enough even if you have an awesome water current in the fish tank.
While all aquarium heaters will turn themselves off once the water has reached a predetermined temperature, if you place a too high wattage heater in a too small fish tank, say a 300w heater in a 5-gallon tank, this might result in the heater being too hot to touch for the fish. Another down side of having a too high wattage heater for a too small tank is the heater will heat the water up to the temperature you set way too fast. It will result in too frequent on and off of the heater. The top reason for most break-downs of aquarium heaters is the result of too frequent ons and offs. It can mean shorter life for the heater if the heater’s wattage is too high for the fish tank.
Installing a proper aquarium heater in your tropical fish tank is essential for the well-being of your tropical fish. You should check the water temperature every time you visit your aquarium as part of the routine in order to notice any problem or malfunction in time. The electricity bill will only be a few bucks a month, because the aquarium heater will not be always on. It is absolutely worth the cost.