A Guide to Aquarium Heater Sizes - The Spruce

A good rule of thumb to determine what size heater you may need for your small aquarium is:
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Partially submersible fish tank heater that includes built-in reflective technology that mirrors surrounding colors so it blends in to the aquarium for both aesthetic purposes and for the safety of your fish. It is shock resistant with borosilicate glass and has a high-density ceramic heat stick for durability. It’s a slim tube with a small profile. It’s easy to install and offers four sizes starting at 50 watts and going up to 200 watts in 50 watt increments.
Find the right size of heater for your aquarium with this handy heater size guide.
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To calculate the size of [tag-ice]aquarium heater[/tag-ice] needed you calculate how many gallons of water are in the aquarium, do not worry about displacement and then multiply this by five. Therefore if you have a 50 gallon aquarium the heating requirement is 250 watts. Not sure what size heater to get for your aquarium? The  makes it easy to choose the  for your aquarium and usual room temperature.
Photo provided by FlickrWith aquariums also coming in so many different shapes and sizes you are going to need to calculate the size of aquarium heater needed.
Photo provided by FlickrAquarium Heater Size
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For those who hate tables but don't mind looking over graphs I have converted the data just for you. A quick glance is all it takes to find the perfect aquarium heater size for your fish tank. Aqueon offers an assortment of heaters that provide the warmth essential to tropical fish’s survival and overall wellbeing. Heaters are built with different wattages, so it is imperative choose a heater that best fits the aquarium size. Review a heater wattage and aquarium size comparison chart to ensure the appropriate heater is installed inside the aquarium. It is also suggested to do research on the type of fish inside the aquarium so that the water temperature is maintained at a level that the fish breed thrives. I cannot stress enough that the wattage of your aquarium heater is not the only factor for sizes. Cheaper models such as the Tetra HT cannot heat anywhere near Eheim or the Fluval E series heater. Only go for cheap heaters as back ups. Heaters can be adjustable or preset to heat up to a certain temperature or for specific aquarium sizes. Preset heaters require no adjustment and have been calibrated to 78°F. Adjustable heaters have manual temperature knob that ranges from 68° to 88°F. It is important to understand whether or not the aquarium heater is programmed to turn off when not fully immersed in water, which is helpful during water changes when the water level goes very low. Some heaters can malfunction if not designed to withstand being out of water. Carefully chose the heater that works best for the situation.I went with a heater sized for an 80-100 gallon aquarium in my 40 gallon wash. Figured better to be oversized if I wanted to maintain ferment temps in -30c weather.So let’s say, for example, a 50-watt heater will heat properly for an aquarium with about 10 to 15 gallons. It’s a known fact that some aquarium heaters work better than others depending on the aquarium size. So, today we’ll take a look at what makes a good aquarium heater and some of my recommendations.