Review on 🐠 SZELAM Submersible Aquarium Heater 100W 300W 500W - Fish Tank Heater with Dual Temperature Displays and External Intelligent LED Digital Temperature Controller - 2 Suction Cups - Ideal for 26-132 Gallon Tanks by Kim Navarro

I had the same results as other reviewers and was about to return the product. Due diligence indicates that I have read the attached instructions more carefully than I initially did; where I noticed the "high current" requirement. Now that the setting is corrected the 300w unit works very well and heats the water very quickly. I also use an 85 gallon aquaponic setup. It quickly heats water (85 gallons), 100 pounds of media, plants and gear. Almost too fast for the fish to adjust properly. 65*F to 76*F in about 4 hours at 65*F ambient temperature and maintains that temperature with seemingly little effort. The only remaining problem is that the device needs to be calibrated. reads 10*F lower than actual water temperature. Set Water Need70*F to 80*F. Not too much of a problem given the alternative temperature gauges. Can't comment on the durability of the device at the moment, but I'll try to keep that in mind if/if I order another one.