SZELAM Submersible Aquarium Heater,100W Fish Tank Heater,Intelligent Temp Probe with External Temperature Controller and Dual Temperature Display,Suitable for Marine Saltwater and Freshwater

This works to keep my aquarium at the right temperature. Make sure the probe in in the water or it will keep heating the water hotter and hotter.

Instead of an aquarium, I used these to thaw out 20-gallon half-barrels in which there are overwintering hardy water lilies and water lotus tubers. After temperatures dropped to and below zero, a couple inches of ice developed on top of the water, even inside the garage where the half-barrels are stored. If the ice reaches my plants/tubers, they will die. After breaking the ice, I was able to adhere these heaters to the plastic liner inside each half-barrel, set the thermostat to 68 F (lowest setting) and thaw all of the ice in a matter of hours. (In the photo, the top container has not had a heater in it for very long, so there is still plenty of ice.) After that, I turned off the heaters again. These are very easy to set up and use! Great product!

The thermocouple for this failed after a couple of months. It started to read much higher than the actual water temperature so the heater would not turn on. This gap between actual temp and a water temp continued to increase until complete failure. Thank goodness I still had a tank thermometer to notice the issue. Otherwise my fish would have been goners. Avoid this product.

Very good aquarium heater, excellent having a sensor which displays existing water temp as well as desired. Worth the money, too bad I bought on Amazon rather than a legit retailer who is a contributing part of local economy.

I’ve now had this for over a year and have had no issues other than the suction cups.

This is probably one of the best heaters with digital display for tempatures. I would have totally kept this heater, but did not fit thru hole in hood for biocube 32 gal. I also love that it is a quartz heat element.

I use these to heat the water in buckets when doing a water change, where the built-in temp probe and external controller are necessary features. They work great. They are actually glass heaters (I would prefer a metal case), but the protective plastic shell has worked well so far to prevent breakage when stored, dropped in buckets, etc.

I observed that it had an external temperature probe and was hopeful about this design feature, but when placed in water the measured temperature fluctuated wildly up and down around 3°, too frequently turning the unit on and off (several times a minute). This is flat out poor engineering. No hysteresis designed in.

Failed after a few months and a bunch of stuff died in my tank