Review on 🐠 Mylivell Submersible Auto Thermostat Fish Tank Water Heater - Adjustable Temperature, Suction Cups - Pack of 2 by Angelica Obegi

Don't believe the ads! The 100 watts were advertised for 45-75 gallons. I bought two to have a backup for my 29 gallon and I got lucky. After trying just one at 80 degrees for several days, I realized this wasn't going to work. If you raise it to 90 it will be 80 but it won't stay. At times it dropped to 78 and there were cold spots in the tank. Adding a second heater worked: 80 was 80 at a constant temperature. I wish I had bought 200 watts for my 29 gallons.