Tetra 26446 HT Submersible Aquarium Heater With Electronic Thermostat, 100-Watt, Multicolor, 10-30 Gallon

I have a few of these in use and haven’t had one fail yet. Most mainstream brands still use bimetallic strip thermostats in most of their aquarium heaters. These Tetra heaters use an electronic thermostat instead, which should reduce potential failure points by eliminating both the moving parts of a bimetallic strip, and the temperature control knob, which is a point on other heaters that can allow water ingress. On paper, that makes them a bit more robust than the traditional design.The main drawback is that these are fixed to around 78°F. If you need to run a tank hotter—into the mid-80s for disease treatment, for example—these won’t do the job.That said, for most people and most setups, these heaters are perfectly adequate, especially at the price point.If you need more flexibility or want extra peace of mind, I’d suggest looking at some of the heaters from Chinese brands with external digital controllers. Even better: pair your heater with an external temperature controller. That way, both the heater and the controller would need to fail at once to overheat your tank. Ideally, you’d run two smaller heaters, each on its own controller, to provide redundancy for both stuck-on and stuck-off failures.Of course, by the time you buy all that, you're looking at a setup that costs about six times more than one of these.So it really just comes down to where you want to land on the cost vs. risk spectrum.For a basic, inexpensive heater, these have done the job just fine for me.

Heats quickly, evenly, and maintains the tank temperature. We have a 20gal tank and this keeps it at a consistent 76 degrees (despite air around tank being below 70 degrees)

Keeps my 40 gallon tank at the perfect temperature.

I put it in a 20 gallon fish tank and it consistently kept the water at about 78 degrees F. That’s exactly what they claim so can’t complain. It is very compact and hides well if you don’t want to see it in the tank. It just wouldn’t cut it exactly when I upsized to 29 gallons so bought a more powerful one.

Es bastante pequeño. Par pesceras muy pequeñas porque mi pescera le quedó grande . Pero si calienta

I had three of this because the first one had worked well on a betta tank, so I added two more in January 2025 to another betta tank and a tetra tank. Shortly thereafter my betta, who had lived in a bowl with an under-substrate heater and no filtration for over a year and who I had just moved into a cycled 5 gallon AIO tank, died. I didn’t think much of it because, after all, I’d had him a while, but he had been super healthy until I put him in the new tank. So I got another betta. Within a week he was also dead. Tested my water and it was fine. I was super perplexed. Until one day when walking by the still-running but fish-free tank, I noticed that the temp was in the 90s. It was WARM TO THE TOUCH. So apparently this heater had been intermittently spiking super high temps and boiling my fish, but I just hadn’t happened to look at the temp when it was happening. So needless to say I do NOT recommend this product, even though my remaining two were working fine (and of course I have now replaced all three). I will NEVER trust a tetra heater in one of my tanks again. Super disappointed that I didn’t notice sooner and that two fish had to die for me to figure this out. But hopefully you can prevent that from happening to your fish by buying a different brand!

Works well

It's great because you don't have to keep tweaking the temperature dial like on other aquarium heaters which are so difficult to get right. Mine keeps the water steady at 76.7F all the time.