I usually use EHEIM Jager 100 watt aquarium heaters in my aquariums. While I haven't had any issues with the Jager heater, it lacks some basic features. It has a digital temp gauge on the heater which I believe is accurate. If you hesitate between 50W or 100W, choose 100W. The lower the wattage, the longer it takes for the tank to heat up, and if you ever want a bigger tank, you'll need to upgrade. The price of this item seems to fluctuate between 17.59 and 25.99. If it's under $20, it's worth it.
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