Most aquarists think of heaters as one of the easiest parts of this hobby. After all, they all heat, it’s hard to have one that is too weak, and most will do very well for years without giving you any trouble.
However, over the years I have come to realize how flawed this mindset is. The reality is that heaters are the number one cause of tank crashes. In my personal tanks, the tanks at the store, customers’ tanks, and service clients’ tanks, the most frequent major problem I have encountered are heaters failing. Usually, they fail on. I’ve lost entire setups to “properly-sized” heaters failing on.
Most people’s first thought is, “Okay then, what’s the most reliable heater? I’ll just get that one.” I have my preferences, and you can read about them in my article on Heaters. But the truth is that ALL heaters can fail, even the almighty Eheim. No matter what your preference is, or what the guy at the fish store tells you, or even what I’ll tell you is my favorite, they ALL can fail. No heater can be trusted.
I lost my first reef to a heater failing on. I had a huge bubble tip anemone, clownfish, nice shrimp, and a nice assortment of corals. Everything had been doing really well (although I wouldn’t admit it to myself that I had an algae problem). I came home one day and the anemone was gaping open. I looked closer and saw a dead shrimp and the dead clownfish. The more I looked, the more things I found dead. It was a horrible day. That was only a 29-gallon. I’ve had customers have MUCH larger tanks crash just because the heater failed on.
This isn’t just an issue for saltwater either. Although there is a little more room for error in freshwater, most heaters are more than strong enough to lethally overheat freshwater tanks as well. I still hate to think about a great group of killifish I had that I lost when the heater failed on.
So What Can You Do?
The best thing you can do is have redundancy protecting your tank from overheating. The article on Heaters describes using only about 2 watts per gallon and splitting that into separate heaters, but the best thing you can do is put your heater(s) on a controller. Set the controller to your desired temperature and set your heaters for only about 2 degrees warmer. This way, the heaters will be on when the controller turns them on, but the heaters will turn off if the controller tries to keep them on when they should be off (such as if the temperature probe comes out of the water). Most importantly, if/when a heater fails on, the controller will turn it off and save your entire tank!
It’s not worth losing your entire tank of fish over a heater that probably didn’t cost you much more than $50. The damage done can be bad enough in a small freshwater tank, and yet some people trust an oversized heater on large reef tanks! And this is just talking about the dollar value of the livestock. I think we can all agree there’s much more to losing an entire setup than just the dollar value.
I’ve used and been very happy with the InkBird controller. It has more features than some, including setting the amount of temperature swing between the heater turning on and off, setting alarm temperatures to alert you if the tank gets too hot or too cold, and it has two outlets. It also has a large display that’s easy to read as you pass by the tank so you can easily do a double-check any time.