What Should I Consider When Buying a Fish Tank Heater?

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  • Written By: Sonal Panse
  • Edited By: Bronwyn Harris
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  • Last Modified Date: 07 November 2019
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Fish are cold-blooded creatures; their internal body temperatures vary in tune external temperature changes. If there are too many temperature fluctuations, however, the fish experience stress and become susceptible to disease or die. To avoid this, fish tank heaters are installed in fish tanks.

A fish tank heater keeps the water temperature stable and suitable to the requirements of the fish species in the aquarium. Temperature requirements may vary according to the fish type. Before buying a heater for your fish tank, find out what a specific fish breed needs.

A saltwater fish tank kept in a cold room will require more heating than a saltwater tank kept in a warm room. Find out what the exact temperature is in the area where the tank is placed. Subtract the required aquarium temperature from the room temperature. The resulting number is the amount of heater wattage needed. For every gallon, there should be a minimum of 4-5 watts of heat.

The size of the saltwater tank must also be considered when buying a fish tank heater. A small fishbowl or tank can do with a heater with a small wattage. A larger tank will require a heater with more power, or better yet, two heaters at opposite ends to distribute heat evenly. A spare heater is a good idea, in case one breaks down.


Fish tank heaters can be purchased at a fish tank supplies shop. Many different styles and types are available. Two of the standard types are hang-on heaters and submersible heaters.

The hangon types are attached to an upper tank edge, with the controls above water and the glass-encased electric part underwater. The submersible types are waterproof and can be submerged into the tank. Submersible heaters are better as they are more efficient, reliable and safe.

Buy the best quality fish tank heater from a reputed company. Install it near the filter, as this is where there is a good flow of water, and leave on for an entire day to stabilize the water temperature. Never switch on a heater out of water and never handle it before it is unplugged.

The fish tank heater will have a thermometer attached. If not, get a separate one. Monitor the salt water tank temperature at regular intervals to make sure there are no major fluctuations. A good tank heater will last a long time and, with a proper, stable temperature in the saltwater fish tank, the pet fish ought to be in fine shape.


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Post 3

@Iluviaporos - I would also suggest that people do a trail run for a while before they put any fish and especially any coral into their tank. Live rock and corals are expensive, and even plants for freshwater tanks can be expensive.

You want to run your fish tank water heater for a few days, testing the water in different places to make sure the temperature is even and holding steady at the range that you need.

A failed fish tank is expensive, and also very sad. Make sure you have backups for your heater as well. If the power goes out, how are you going to heat your fish tank? It depends on you to make sure you have the answer to that question.

Post 2

@bythewell - It can be a good idea to install a sump tank if you want to stock too many corals and fish into too small a space for them, but if you only have a few plants or fish and just want to keep them safely in a small area you don't need to get a sump tank.

There are other ways of ensuring the water is going to be warm enough. First, make sure your lights aren't already heating the water to the point where it gets too warm. Lights and aquarium heater together can be too much sometimes.

Next, make sure your heater has a switch so it can turn itself off if it gets too hot.


finally, position your heater in the right place. It might be best next to the pump, for example, so the water near it is always on the move.

But, really, if you are just beginning, try to get the biggest tank you can. It seems counter intuitive, but larger aquariums are easier to keep than smaller ones, as there is more room for error with that amount of water.

Post 1

If you have a small tank, you might consider installing the heater in the sump tank. This is a tank you use to house extra water, but which doesn't contain much, if any animals or plants. This way you might have quite a small display tank, but stock it with more animals than it would normally be able to contain, because the sump tank (which is usually hidden somewhere in the stand or behind the display tank) is sharing the load of contaminants and things like that.

If you heat a small tank directly, even with a small heater, it can be difficult to keep the water temperature even as it might not circulate enough to cool down the area

around the heater.

But, if you heat the sump tank instead, the water from there will circulate to the tank and ensure a steady flow of warm water to your corals and fish.

A sump tank seems like a complicated addition to an aquarium, but it is actually a way of making the whole thing easy to handle.

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