Aquarium heaters - do I need two?

[Theresa_M]

I have a 75 long with a nice Eheim heater. I have the thermometer set up on the complete opposite side of the tank to monitor the temp.  This is a newer tank - about 5 weeks now. The temp has maintained at what I've set the heater to. However, I have seen recommendations that two heaters for a tank of this size is ideal. Thoughts on that?

Seems to be working fine as is, but would it increase the life span of the heated??

[FrozenFins]

If the water tempeture is what you are wanting then a second heater is not mandatory. I wouldn't get another one if the on you already have is doing the job you want it to.

[Kirsten]

Not necessary if you're getting the temps you want throughout the tank. Me, I have 2 small heaters in each tank because my water circulation isn't that great and I keep my house pretty cool in the winter. Having 2 means neither of them have to work as hard to heat the tank, which will hopefully save them from burning out as fast, but when one does go, there's a backup. Plus it's nice to have an extra one to throw in a quarantine tank if needed. 

[gardenman]

Two are better than one if the survival of your fish depends on the tank temperature being significantly higher than the ambient temperature in the room where the tank is being kept. Aquarium heaters fail on a fairly regular basis, so having a backup heater can be wise. Keeping that backup heater set just below the temp the other one is set for  should prevent your fish from getting too cold. Of course, having two heaters doubles the chances that one could fail in the on mode and cook your fish. (Which happens from time to time.) Aquarium heaters are one of those products that seem to have gotten worse over time. Heaters from fifty years ago were largely immortal. Modern ones seem to fail far more frequently. 

I'm kind of intrigued by the sous vide cookers that are out there as an aquarium heater. They're made for the food industry and are reportedly extremely accurate. They circulate water also instead of just radiating heat. Long term durability would be an issue as you'd want one running 24/7, but that technology would be intriguing to bring to the aquarium hobby. Some of the sous vide cookers claim to run for 10,000 hours or more straight and be accurate to a very fine margin (less than one degree) and have up to 1200 watts of power. It's not easy to find a 1200 watt aquarium heater. Most aquarium heaters top out at 300 watts. Some sous vide cookers have lower temperature ranges that come pretty close to what you want in an aquarium heater. Marrying the two technologies might be a good new tool for the aquarium hobby. A heater that circulates the heated water, has up to four times the wattage of a typical aquarium heater, is long lasting, extremely accurate, and even capable of being monitored by Wi-Fi. It could be a pretty neat product.

[Colu]

On larger tanks it better to have two heaters in case one fails and it keeps it at a more stayable temperature haveing a heater at each end of the tank

Edited January 18, 2021 by Colu

[redmare]

I think if you have good water flow you don't need two. It can be good to have a backup on hand, not necessarily in the tank, in case of a failure. It also might be worth having two if you're trying to raise your temperature significantly from the room- maybe over 10 degrees, or if you're keeping something like discus which can be more picky about the temp.

[lefty o]

if your temp is good from end to end of the tank, you dont absolutely need 2. my thoughts on heaters are, it is better to use 2 undersized heaters, than 1 big enough heater. with 2, if one sticks on it may get warm but not likely hot enough to cook the fish. with a single heater that is big enough by itself, there is a potential if it sticks on of it getting the water too hot. that said only on my 120g have i ever run 2 heaters. on the smaller tanks i tend to run single heaters that are slightly under the recommended size. there are no absolutes with aquariums, just hedge your bets the best you can.