Tetra(R) HT Submersible Aquarium Heater

Works well. I was nervous at first because there was no device to see temperature but its not needed when you have a sticker thermostat. The speed of the temp rising was good to not shock my betta. It took about 24 hours to get to temperature. It had no smell when it started to heat up. It stuck right to glass with no issues, unlike ones I've had in the past, with other company's. When its time to clean it a quick wipe down will do the trick making keeping it clean very easy. It was smaller in size so not too thick and hides off to the side.

I’m using the Tetra HT 50-watt heater in a 5-gallon tank, and it’s been excellent so far. The built-in thermostat keeps the water right around 78°F, and the temperature stays steady day and night without needing to adjust anything. I checked it against a thermometer and it’s always within about a degree. Installation was easy — just stick it to the glass with the suction cups and plug it in. The size is perfect for a small tank; it tucks neatly behind a plant and doesn’t get in the way. The indicator light is a nice touch so you know when it’s heating. For a small setup like a 5-gallon betta or shrimp tank, this heater is exactly what you need: simple, quiet, and dependable. Great value for the price.

So far this heater is working great. Keeps my 20 gallon tank at a steady 78° without having to mess with a finicky dial. You don't have to remember which way to turn the dial taking all the guess work out. It's small size takes up less room as well.

Well this heater finally broke after two years. Which honestly isn't super durable, I guess you get what you pay for. The light no longer comes on and it doesn't heat the water at all. But it did work perfectly for two years so I'm lukewarm on it. Like my tank water at the moment.

Easy and uncomplicated, just the way I like it. Either as a standalone heater as in my 30 gallon tank or working in tandem on a thermostat as in my 55 gallon tank they are just dependable inexpensive heaters. I don't know how old my last one was before I replaced it but it had been used for a while before it came to me with the tank I bought and I was so impressed with it's dependability I replaced it with another. Funny thing is it never did fail, I was just being proactive as I didn't know it's age. These are my heaters now. I will say I did take the old suction cup and added it to the new heater. It would be nice if they came with two suction cups.

Many people that are rating this product with a 1 or 2 star clearly are not using it right, saying it is going out or not heating hot enough. To use this heater properly, you must sit the heater in the aquarium water for 30 minutes before even plugging it in. This is to set the thermostat inside the heater. Also, you must place the heater set up 90 degrees or laying flat parallel with the bottom of the tank. Another reason it may stop working is, once you turn off the heater you must leave it in the water for 15 minutes before taking it out. Bottom line is, this is a great heater. I use 3 of them total, one for a 10 gallon saltwater nano reef, one for a 10 gallon freshwater aquarium, and one to heat up my water change water. This is one of the best compact heaters I have used, compared to two other more expensive heaters. This is also definitely the cheapest place to find the heater (on amazon), in my local fish stores it runs $17. Ignore the reviews by people that probably didn't even read the instructions before sticking it in their tank and saying it doesn't work right. No adjustments need to be made with this heater and that is one of the greatest things about it also. Pros: Red light when heating Green light when temperature is correct Small and compact Cheap price Good quality Fully Submersible Heats up to 10 gallons Consistent temperature Rubber protects the glass heating tube Cons: Cannot change the temperature if desired.

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!

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.