Review on 🌡️ Aqueon 7.5 Watts Flat Submersible Heater by Leslie Harris

I bought a 7.5W heater for a 5G faucet aquarium. At first it worked quite well and my aquarium heated up 2 degrees above room temperature (e.g. when the room was 78, the thermometer showed 80). However, after almost 3 weeks I did a partial water change in my aquarium and noticed an oily residue on the water surface. Upon closer inspection, I found that the residue came from the heater (see picture). Not sure what it is, but it's oily when touched and burns the skin (like a chemical burn). I quickly removed the heater and kept a close eye on my fish and snails. I'll be so upset when they die. I am grateful to Revane for processing my return so quickly and am now looking for a properly manufactured heater.